unlocking with T-Mobile
T-Mobile charge a flat fee of £20.42 for unlocking phones. This can take 20 days (or up to 60 days for a Samsung). For existing customers you must have had an account for at least 6 months, pay monthly customers must have an account balance of zero - everything should be paid and up to date.
The phone number to request a "network subsidy code" is 0845 412 5000 . Or you can fill in your details here.
T-Mobile states that it will be sent by post up to 28 days later though by some accounts it doesn't usually take that long.