People can text me but I cannot receive my validation code or other messages from e2Campus.

There are two types of text messaging:

1. Mobile Originated (mobile-to-mobile, sending a text message from one phone to another)
2. Mobile Terminated (a non-cellphone to a cell phone)

You may be able to receive mobile-to-mobile text messages, but your account may not allow for mobile-terminated messages. You may need to change your plan with your carrier in order to receive mobile-terminated messages.

Some carriers provide a way to send a text message to a phone by sending an email to @.com. Example: 5072225455@messaging.springpcs.com. If this works for your phone, you can still sign up using the Email-Only method.

My carrier is not listed.

e2Campus supports a number of wireless carriers. The list of carriers can be found on the e2Campus site. There is also a link there to contact them about initiating coverage with your wireless provider.