Using an iPhone 5, I receive spam text messages that do not have a number, but that are from an email address that normally/usually change every time. I believe they are being sent to my phone number's email addres (phonenumber)@vtext.com. After receiving the text messages, I block the caller through iOS 7 setting (Contact>i button>Scroll down and hit "Block this Caller"). However, spam keeps coming through.

They are relatively different messages with different formats but are all of similar content.

Any ideas on how to stop the spam or change my phone number email address?