I was a loyal orange user right from the first time I ever had a contract phone and got a free 3210 on an everyday 50 tariff! I stayed with them because I was so impressed with their customer service.
I stayed with them until the N-gage came out because it looked like a cool phone until I realised I had to use it like a taco strapped to the side of my head and the fact it wasn't very good. I had to move to o2 for that phone but because they didn't send me a game that was promised I left, as it was in their terms, and came back to orange and got my very first windows mobile phone, a spv e200. After the first year the fun began.
I tried to get an upgrade to the m2000, and it took orange FOREVER to get this out to the public, even though I was willing to pay for it. It took a while and with the good people on here someone a bit higher up in orange apologised and gave me the handset for free. So I had a good year of using it (but not for data!) and then managed to get an o2 exec when they majorly balzed up and mispriced the phone. With that tariff I had an incredible 5mb of data a month!
In between I then sold my old e200 and m2000 and bought a c500 on payg. So at this point I was swapping my o sim between the two handsets depending on where I was going etc, and my work bought us all c500's about 2 months after buying mine. So that went back on ebay and I was using two mobiles swapping sims as necessary.
The new m3100 came out and they wanted me to pay an astronomical fee, and wouldn't do any data packages, and then I heard on here that T had started to do data packages. So this combined with ever declining customer service (which from being the best went very much to the point I was shouting at O) I went to t-mobile. Never looked back since.
I even get half price line rental now as my fiancée used to work for T and gets half price line rental and had a "spare line" I could port to! (it was spare because it was cheap and effectively gave her a very very cheap free phone every 12 months in addition to her main phone.
Stupid thing about that was I wasn't allowed to move my phone no directly across. I had to change to virgin and back again!
Dont think I will ever leave t-mobile now due to the half price line rental, not unless they manage to really cock it all up. From being on one2one as my first ever phone and their customer service leaving a lot to be desired and now t-mobile are arguably the best operator out there I would say they are just going from strength to strength. Im very happy with them.
( no I dont work for them but if anyone on here does and wants to give me another phone, please feel free!!!!

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Phill