Go ahead and file with donotcall.gov, but also call your cell phone provider!
Some providers like Sprint have registries that keep track of numbers that are "pestering their customers" and try to block them from their entire network. Others may not have a system like this in place. You can either call your provider and file a complaint, or for AT&T, do the following:
Send a text with the problem number to 7726. That's a free message since it's an AT&T system. They keep track of this and block problem numbers from their WHOLE network, so it won't bother you or anyone else again.