Not getting Voicemails

It has been a month now and I still am unable to get voicemails. I have had this phone number for about 15 years and have never had this problem. TMobile has not been very helpful and the customer service does not exist. I have had 2 tickets opened, and nothing. No one calls me with an update. My voicemail began to work yesterday, but today it is not. I am absolutley furious and want to swtich carriers. But of course, I still have to pay full price for a service I am not receiving at the moment.