Mobile number change will cost $15.00 processing fee and it will take effect within 2-4 hours. Kindly note that you may lose your voicemail message, call recordings as these will be deleted as soon as the mobile number change request is submitted. Voicemail PIN will set to default using the last 4 digits of your new number to setup password and greetings again. Call records for the old phone number will no longer be available on My T-Mobile. Don't worry about the card information right now, when it comes time for the payment I have a secure form I can send you for that. All updated now, Please restart your device to activate the service and this may take up to max 2 hours. Once phone turns on please do test your service by calling out. I will appreciate it.