As my post above, I have always warned people about cancelling/upgrading contracts with 3 and making sure it was done properly. Not that I am against them normally as they do give great value for money. Examples:
I have 3 accounts with 3:
-Main phone long term contract, going on 6 years.
-Mobile broadband 1 month rolling contract, going on 18 months.
-Sim only (spare) 1 month rolling contract, going on 4 months, bought as I needed extra minutes at the start of the year, with the intention of cancelling last month when I could upgrade my main contract to a better tariff + SGS2.
Cancelled the spare sim in store 2 weeks ago (well, they phoned CS in India from the store); apparently done, yet a few days later, I got a letter confirming I had upgraded to a higher price plan, but at a cheaper monthly rate. :/ :/ :/ When I called CS, they had to investigate the act of misselling and couldn't confirm the cancellation until it was resolved. Frustrated, I logged a complaint online and a few days ago, got a reply back from 3 apologising and confirming the cancellation with the 30 days notice from my cancellation date. FIngers crossed no issue now!
Mbb - I fancied a new wireless modem and popped into the oxford st store. THe lady said it was fine to "upgrade" the contract with no changes to price plan cost or 5gb allowance. All I would have to do is pay £40 for the new modem, which I was happy with. Paperwork from the day all good. Today my new bill shows that I have apparently downgraded my allowance to 3GB, yet will be paying the same £15 every month. Skipped CS altogether and went straight to logging an online complaint.
Assuming the above are 100% resolved, I still think I will then be ditching them as my service provider and switch to someone else for the SGS2. They can't match the £25/27 a month others are offering it for anyway, even with my loyalty discount.
Anyway, lesson is to double check cancellations/upgrades with them, making sure the paperwork is fine, and sending letters receorded delivery or messaging by email so you have records of everthing communication.