Help with getting online with Sprint PPC 6700- error codes

[DMAC]

I have a problem with my phone accessing the internet on everything except wifi. Long story short, I lost my first phone and was sent a replacement phone. Everything else works fine but when I try to access the internet I keep getting 2 messages - Error code 67: registration failure- pcs vision username and password are incorrect and then another message pops up saying Cannot connect- no modem at above number. I am very new to this phone (only had my first for 2 months) and called Sprint literally 15 times and its been about a week and all they keep doing is issuing help tickets and telling me they will call back. Any suggestions to fix this will be greatly appreciated.