I got a CDMA phone - clean ESN - for use on Virgin Mobile's network. How do I use a different phone instead?

I know very little about cell phone technology, but I read somewhere that with CDMA phones the ESN has to be cloned to a new phone to do this. This LG Rumor Touch isn't cutting it and I'd much rather have a CDMA phone that Virgin doesn't offer. If I could get some links with instructions or if someone would get in touch with me via IM I'd greatly appreciate it.