T-Mobile recently revised their SIM unlock procedure. The real difference is a lesser amount of days of service with them (in good standing) of 40 instead of 90 days. Nonetheless here is some valuable information from a poster over at Howard Forums:

HowardForums: SIM Unlock Policy Changes

SIM Unlock Policy Changes

T-Mobile recently agreed to settle a class action lawsuit, Marlowe v. T-Mobile USA, Inc., which was related to SIM unlock requests. As part of the settlement, several changes will be made to the SIM Subsidy Unlock policy on January 21.

· Eligible postpaid and FlexPay customers will be able to obtain a SIM unlock code after 40 days of service instead of 90 days.

Authorized dealers will continue to contact Customer Service via the Retail Support Line to submit a SIM Subsidy Unlock request for customers or advise customers to call Customer Service.

· Eligible prepaid customers will be able to obtain a SIM unlock code after 60 days of service instead of 90 days, provided they have an account balance of at least $10 or have made a refill within the last 30 days.

· Customers with a past due balance will not be eligible to receive a SIM unlock code unless they bring their account into good standing. Exceptions apply for Business and Government account types and will be listed in the SIM Subsidy Unlock policy.

· Customers with cancelled accounts qualify for a SIM unlock code, provided their account is in good standing with no past-due balance and they had a minimum of 40 days of active service with T-Mobile prior to cancellation.

Customers who paid full retail price for the handset do not need to meet the 40-day requirement.
Former customers whose accounts are not in good standing have the option of paying in full all past-due amounts in order to obtain the SIM unlock code.

Customers can search for SIM Unlock on T-Mobile.com or check the SIM Card Unlock Code FAQs on T-Mobile.com and My T-Mobile (SIM Unlock Code) after January 21 to view the disclosure below.

Disclosure:
If you purchased a wireless phone from T-Mobile, your phone has been programmed with a SIM lock which will prevent the phone from operating with other compatible wireless telephone carrier's services. If you wish to use the phone with the service of another wireless telephone carrier, you must enter a numeric SIM Unlock Code to unlock the phone. For customers with a T-Mobile Postpaid Plan, T-Mobile will provide the SIM Unlock Code upon request to eligible customers, provided the requesting customer has a minimum of 40 days of active service with T-Mobile. For customers with a T-Mobile Prepaid Plan, T-Mobile will provide the SIM Unlock Code upon request to eligible customers, provided the requesting customer has a minimum of 60 days of active service with T-Mobile and either a Prepaid Plan account balance of at least $10.00 or a prior refill within the last 30 days. T-Mobile will provide the SIM Unlock Code upon request to eligible former customers, provided that T-Mobile has such code or can obtain it from the manufacturer. You may request the SIM Unlock Code for your phone, together with instructions for entering the code, by calling T-Mobile customer care at 1-877-453-1304.
Here is a well outlined process of obtaining SIM unlock code, originally posted by former member Ellen.

Quote Originally Posted by Ellen View Post
How to request an unlock code for your Tmobileicon handset:
To receive your unlock request, you must meet the following criteria and this criterion can not be waived.

* (See above paragraph for revised policy changes)

* You must have a Tmobileicon phone number.

* Only one unlock code will be issued per active line within a 90 day period.

* IMEI number must be provided directly from the customers handset (IMEI number can be obtained by pressing *#06# on your handset).

* Handsets that were purchased through eBay, pawnshops, garage sales, or other sources must still meet these requirements.

To obtain your unlock code send the following information via email to: [email protected], or call customer care directly at 1-800-937-8997 to obtain the unlock code. ** When calling you are still required to provide all of the information listed below.

Information needed for unlock code:

* Account holders name (required). xxxxxxxx

* IMEI number (required) *#06# on the mobile handset.

* Account password or the last four of the account holders social security number (required). For prepaid customers this can be the last four of your mobile number To Go pin code number. xxxx

* Customer contact number or email address. xxx-xxx-xxxx, or [email protected]

* Make and model of the mobile handset. (ie: Nokia 6030)

* Carriers name if the handset is from another carrier. ie: AT&Ticon (please note that TMobile is not required to provide unlock requests from other carriers, but has been reported to do so for a few of their customers.)

* Reason for the request. (ie: Going on a trip abroad, or giving the phone to a friend on another network.)

*** Please note that in some cases it may take up to 14 days for TMobile to fulfill your unlock request.
Thanks to Ellen and Howard Forums member Teyong for this useful information.