Verizon is usually willing to work out most issues with you as long as you want to remain a customer. If you are planning on switching providers wait until your contract with Verizon expires (if not you get charged a $150 fee for ending your contract early). If you just want a new phone your best bet is to check with Verizon first.
Every two years you can get a new phone (for the same price you would if you were signing up for service) by extending your contract another two years. If you want to do this (through Verizon) before your 2 years is up I would visit their website (www.verizonwireless.com) or call their 1800 number to speak with a representative about and “early rebate exemption.”
Basically they would give you the new phone discount early and extend your contract (another two years). If you want to just buy a new phone outright (from eBay or another merchant) make sure that it is compatible with Verizon first. They can extend your service onto this phone for a fee (I believe it is $75, but you may want to double check based on your plan)