My husband and I are currently at war with Verizon and had them for around 4 years and it was an amicable relationship up until the last 6 months. They canceled our account and tried to get US to pay for it, lied to us, outright, several times, and when called on it, canceled our contract. It made us smart. We went to another company and so far we're doing well, we can change phones with no problem (not so with Verizon as they don't use removable SIM cards and you have to take your phone in to a store to reprogram it if you lose your data).
The only thing I can tell you is that if you want to change ANYTHING on your plan, get it ALL in writing before you agree to anything. I got this advice from a friend who works in the cell phone biz who doesn't like having to work with Verizon at all. I wish we had known this as it's cost us, to date, over $900 USD to get things sorted. Get everything in writing, even if it's just upgrading your data plan.