Can a service agreement that has been signed and returned be voided by the company because of claiming error in contract?

I recieved a 2 year service agreement in the mail from my cable provider for a $99 package. I signed online through the company site accepting the terms. My bill has reflected a higher chrage of $114. I called the cable company and I was told that the contract that I received was sent in error. That at the time I selected my package I signed (agreed over the phone) to $114 and the $99 package is no longer offered. I have asked that they honor the agreement that I signed and they are refusing. Can they void a signed agreement due to internal error?