I’ve been on Plusnet since they launched their mobile offering, and have been quite happy with the coverage, speeds and service as well.
Currently on 4GB @ £10pm, but spotted the 5GB offer ending soon for the same price. No-brainer to try and upgrade to that 
I rarely reach my current 4GB limit but always nice to have more available.
I’ve been with EE, GiffGaff, Tesco, O2 and am now with Three.
Three have been the best.
EE was way too expensive and their customer service is shocking. I also had to fight to get some money back from them because despite me cancelling my contract they were still taking money from me. I started off on a £10 a month (sim only) contract, and by the end of it was paying almost double due to price rises what seemed like every year. I currently pay three £15 a month for unlimited everything.
I’ve never had any real issue with reception (live in London) and the speeds are good enough for me. My partner is with EE and although the speeds are faster, there’s no real difference in call quality and she pays the same as I do for far less allowances.
I’ve been with Three for the last 8 or 9 years, and that includes working for Vodafone during 3 of those years. Even with staff discount VF was expensive.
I’m paying £20 for unlimited calls and texts, 100GB data and 30GB tethering. The plan includes their free roaming in feel at home countries (can’t remember new name for that)
Signal is generally pretty good. Fast data too. Customer service has been excellent. I have a home signal box in the house, but that’s not a bad reflection on Three - my house is made of concrete and doesn’t get a signal on any network. We also have a box for my wife’s EE work phone
If you ever leave PN mobile, cancel the direct debit, took me 3 months of future charges to get it actually cancelled 
Not really had any issues with 3 save for my old work being in an area covered by an unreliable transmitter (regularly down for maintenance when I’d have no signal). Now I’m nearer home, it’s fine.
I am, however, on Smarty now, who use 3’s network but their pricing structure means I can save a fair bit if I don’t use as much data, and I can buy extra at the same rate if I use more.
I have had an issue with Smarty lately in that you can’t text shortcodes (6 digit numbers) even if you add credit. This means you can’t reply to PayPal fraud detection texts and maybe other banks, or unsubscribe from other messaging subscriptions that you may have been on before switching or signed up elsewhere. They also require a credit card to unblock “adult websites” (which actually include a lot of websites that aren’t particularly adult, e.g. archive.org). After complaining they say you could contact them with another form of ID and that could also work, but they don’t advertise this fact anywhere.
Been on 3 for several years now and even had a few mobile broadband contracts with them. Only real issue i’ve had is on the train where I live, for a few stops you get nothing where people on O2 and Vodafone still have full 4G coverage.
Cant complain about the price of the contract, £18 sim only with unlim mins, texts and 30GB data.
I do use it abroad quite frequently and cant say i’ve had any issues.
Wuntu (haha one, two… I just got that!) has provided quite a few freebies from coffee to pizza that is a nice addition but haven’t had the chance to try the EasyJet upgrade yet. Maybe soon…
Also Go Binge is a nice addition!
I know most people here don’t have good things to say for O2 but personally I have been happy with O2. Their 4G has improved a lot and now calls/texts have never been an issue in London.
I agree network coverage is decent, its customer service that is bad.
I’ve used Three for the past 6 years. (Joined for The One Plan and stayed as they’ve not done anything bad enough for me to leave.) Their 4g speeds are decent but not spectacular. I think the 3g signal is more robust and just as fast 90 per cent of the time so it’s what I use.
I was on their unlimited everything plan for 28 pounds. (12 months SIM only) I don’t use even close to 100GB a month as I have WiFi at home. So after my contract had finished retentions offered me their 100GB and unlimited everything else for £20.00. I grabbed that offer thinking it was a great deal as it was at the time, only for them later that month to offer the same price to new customers. I called to make a complaint as a semi joke and I got offered to cancel my contract for nothing or to continue with the same deal for £18 pounds a month.
The closest network to Monzo would be giffgaff. Great at the start but now just so so. Data speeds are terrible plus the fact that they got rid of their unlimited goodybags and now replaced it with always on goodybags. 
Their community is great. Network signal however is normally excellent.
I am with EE and love their speeds and customer service. I have tried 3 in the best their internet I found terrible. Vodafone have used too and their customer service is bad and I hate not being able to use 2g. 02 are not bad for rural areas.
So to make way for 4g and a change in a TV transmitter, all of a sudden phone signal was not yet good. A call to EE and they said just use the WiFi calling and it won’t be a problem, well yes it will be a problem because it’s not Android or iPhone, a phone call to three, no problem we shall send you a box connect that to your router and you will constantly have a mobile signal. Three is cheap and reliable in my experience. Recently upgraded with them and my bill actually went down with a P20 Pro
Have you got WiFi calling on your phone? You’ve mentioned this device on another thread, but I wondered if there was a reason that you couldn’t use WiFi calling.
I say this because I am tentatively looking at 3 to change from giffgaff. I know my home address will be difficult for signal and because of this I’m not confident about the move. I’m thinking about having the pay as you go bolt on sims for a month to make a judgement.
Does anyone know if 3 restricts who has WiFi calling to particular tariff?? Or is it open to everyone?
My mother doesn’t have a phone with WiFi calling she’s often at mine. I have WiFi calling built in to my phone and have no issues with it.
With three there has been no restrictions with WiFi calling since they launched it officially last year.
I’ve used 3’s WiFi calling on both PAYG and SIM-only contracts, both using the built-in iPhone WiFi Calling and using their inTouch app on Android.
Built in Android WiFi calling works with three as well.
Cool. My Android phone when I had one didn’t support WiFi Calling (thus why I used the inTouch app).
I can’t seem to get WiFi calling to work on my handset.
P.S. Yes I know I’m on WiFi on the picture and not using mobile data. 
Have you checked with Network provider that WiFi calling has been switched on for your number?
On O2 this can be done online or in app. But have to have it on to get it working.
What phone have you got? I assume you have tried airplane mode with wifi on and leaving it for a few minutes?
Yep I’ve tried that, I have a One Plus 3.