You can have the phone flashed to metro from sprint. I have the EVO SHift that I used on SPrint for some time. I recently signed up with Metro and had the EVO flashed. I did it through a company called Flash King out of Tampa, FL, as I am here on vacation. When I signed up at metro, I got a cheap android phone and quickly realized that I hated it. Flash King flashed the EVO and calle dtheir rep at Metro corporate to let them know I switched my phone. It downgraded me to the $40 plan, and as far as Metro knows, I am using a non-smart phone with web capabilities. Saved me the $10 a month and I can still use all of the features I used on sprint. They dont have a website, but their facebook page is Flash King - Professional Services - Tampa, FL | Facebook
Give them a call, ask for Tony, he is very helpful.