verizon/ billing error

Last October 2006, I had to replace a faulty verizon Lazer cell phone . Verizon shipped via Fed ex and requested return of old phone which was returned in a matter of 2 days, however now I am receiving bills from verizon for some $300.00 as they are reporting they did not receive package from Fed-ex

Even with tracking numbers , Fed ex cannot track as their contract with verizon has a 22 day limit .Repeated phone calls to verizon and Fed have failed to resolve the problem of lost phone . One would think that Verizon should have notified the consumer within the 22 day time frame that phone did not arrive . There has been a 3 month delay in notifying me of a problem. Should not Verizon be dealing with Fed-ex. ?

Verizon threatening with shut off of cell phone . This is certainly not a good promotion for Verizon and I will have a difficult time recommending their service to family, friends and peers. Any advice would be welcome .