Well I figured I would put in my 2 cents here, I don't defend any of the large networks carriers, but I can tell you this, I have had them all at one time in my life, and no matter which one you go to, you will have one issue or another, they all have their issues and areas where their service is better than others. If you check the Verizon section you will see many threads about this same very issue, members complaining about service from Verizon and their customer support. So the bottom line is usually depends on where you live, and researching the carriers that have the best coverage for that particular area, now grant you, service could be good for years in that area and then goes downhill, well that could be due to many factors, you changed your phone, which does not have good radio signal, they could of changed a tower in your proximity, another building or hardware was put up in your area that could be interfering and there could be many more other reasons and factors. Each end users location vary and are different.
This is what I would do before I were to change my carrier, as I have been in this position a few times and as we always see the grass as being greener on the other side, this is not always the case, I would either find someone that lives in my area and ask questions about there cell phone coverage, I would also try different carriers for a few weeks, and use the buyers remorse option, if their coverage was not any better. I would not be so quick to switch carriers, as I can tell you this, there will be somewhere else you will have an issue with if it is not your home or local area. If you read this thread a little you will see 2 members from the Phoenix area and yet one has no issues and the other drops calls, I would test other carriers before you switch and using the 30 policy by most.
Just my 2 Cents for what it is worth.
FWIW, you have the option on roaming on the Verizon network with Sprint, Sprint's Roaming Contract with Verizon...