Question [Q] Motorola Droid X MMS messaging problem

I just got this as my first smartphone, so excuse the newbie! I just bought this phone from The Phone Cellar on eBay. I am on Page Plus' Talk n Text 1200 Plan. I cannot seem to send MMS messages on my phone and wonder if this is an issue with my plan or with my phone.

When I try to send a text message, the phone automatically tries to send it as MMS. I get the error "No data connection. Please check your MMS APN configuration in mobile network settings." But on the phone settings page, the only thing that shows up under Mobile Networks is a System Select option -- either "Home Only", or "Automatic." (I've tried both, and I still can't send MMS).

After I try to send a text, it fails, shows the error message, and the phone then reverts to some non-MMS format (the "MMS" indicator goes off - maybe that's SMS?). I can then send a text. So every time I want to send a text, I first just send a one-letter text that fails and then send the text I want to send! Picture messages never work.

I called Page Plus and they reset all the data features on my account and re-provisioned my device into the network, but that didn't work.

Any help is greatly appreciated!