I have to agree, bad choice for trainer. Cubs are slow flying planes but have some characteristics that make them difficult to handle on the ground.

Were you plugging directly into the receiver to check the channel, or going thru the "Y" harness? If the latter, then it sounds like the harness is bad. If the former, then you're going shopping for a new receiver.

I hate to say it but you're learing a valuable lesson about aviation. Untill you've got enough experience under your belt, IMHO, you should always buy either:
1. Used stuff you've personally seen fly so you know it all works or
2. Brand new stuff with a warranty, so the MFR will help you out if stuff dosen't work right.

And I would further suggest your first plane come from either a fellow club member, or a local hobby shop reccomended by a fellow club member. Mail order and Internet can be much cheaper, but it's not worth it to save money if you're pulling your hair out trying to figure out a problem that could be solved with a simple visit to a shop or your field. A couple minutes of advice can save much fretting and wringing of hands and gnashing of teeth. And cursing of SO's, pets, etc you get the idea.

Andy