Panasonic KX-TG5421 Cordless Phone "straight talk voice mail" Questions

I have a ZTE phone from straight talk and it says my voice mail is full but will not let me pick up my messages. How do I retrieve them Call the customer service dept of your service provider.

...straight to my voicemail. Is this possible? If you have 3 way calling ,you should be able to do that, as long as you are talking voicemail and not the answering machine, flash your receiver and dial ...

...straight to voice mail. I read about other problems with this phone on other websites. I always research before I buy something, but, this was an impulse buy because it was such a good price, and I ...