Poor service connection

[VRader0424]

I've had Verizon for several years with no issues until  I got a new phone a few months ago. Now I often receive "server unavailable" messages when trying to make calls and cannot make or receive calls or texts more than half of the time. It doesn't matter where I am, at home or out, same issue. Verizon store basically said it's because I'm a prepaid customer and won't get the best connection, but I've been prepaid for years and only began having this issue recently. My husband also has prepaid Verizon and his works just fine. Anyone have any ideas?? I've tried taking sim card out and putting back in. Doesn't seem to help.