T Mobile Pulse going straight to voicemail

[Guest browning guard]

Hi there. Absolute newcomer looking for some help. On my second pulse now as previous one replaced by t mobile and I can't seem to find any thread with the same problem. Haven't made any changes to standard phone apart from downloading some apps. Quite suddenly all my calls are going straight to voicemail and no changes have been made to the settings - they have been checked and are correct. I can make calls and receive texts including those that say I have a missed call but all the caller hears is a beep and straight to my personal message. Any suggestions before I return this phone too? Thanks for your help!