Hi there! We'll definitely be sorry to see you go, but I'm even more sorry to hear you've been having such a tough time reaching out. To cancel service on a postpaid plan, you do need to speak with a Customer Care representative. If you still have a device with a T-Mobile SIM and any roaming signal at all, you can contact us by dialing +1-505-998-3793. All calls made to this number from a T-Mobile handset are free from roaming, airtime, or long distance charges. If you don't have your T-Mobile device and SIM any longer, you can still dial this number from any phone - but please be advised that calls made to this number from landlines and non-T-Mobile phones will result in international long distance charges and possible additional local charges.
Also, I'm sorry to be the bearer of bad news, but once your line is cancelled, the voice mail service will be cancelled as well, so there's no opportunity to set up an outgoing message.