I like the EnV phone because its really great for texting but I have a Nextel service. Is there any way that I can keep my Nextel service while using the EnV?

No, Nextel uses a technology called iDen. Verizon (and sprint) use CDMA. No sim cards with CDMA. I had nextel, but I was sick of them billing me hundreds a month for no reason, I switched to veirizon. Much better. They also have Walkey-Talkey phones if thats what you need.