- Click on "Buy SIM now" and order the SIM card (costs $15, but they often have a discount on it)
- When you receive the SIM card, take down your phone's IMEI # (usually found under the battery, in the phone's settings menu, or or on the box the phone came in)
- Be sure your postpaid account is fully paid (balance of zero)
- Turn off your phone and remove the SIM, insert the new SIM but keep the phone off
- Go to http://prepaid-phones.t-mobile.com/prepaid-activate and activate the new SIM -- IMPORTANT -- in the section where it asks whether you want to keep your current cell # select 'No' (you have to make the switch over the phone with T-Mo).
****If you are not currently on T-Mobile, select 'Yes' to keep your current cell #.
- Select the plan, it's sort of in the middle of the list of options, and pay the initial $30 monthly fee
- You will be assigned a new phone #, take this down
- Turn on the phone with your new SIM card in it, this will have the new cell #
- Call T-Mo support 877-453-1304 and ask for a Prepaid representative (if they ask why you're calling, say you want to transfer your postpaid phone number to your prepaid account)
- Ask the Prepaid representative to transfer your postpaid phone number to your prepaid account, emphasize that you have an existing prepaid account that you want to use
- They say the phone # switch takes 24 hours, but mine came through in just a few minutes! You may need to reboot the phone after the call with support. You'll get a text message once the switch is completed.
If you're not on T-Mobile but have or purchase an unlocked cell that is compatible with T-Mobile (be careful with the data specifications, since not all phones are compatible with T-Mo 3G and higher data speeds), it should be the same process except when activating online you can request the port of your current number online instead of having to call T-Mo. You will also need to request that your phone be unlocked by your current carrier before switching.