You'll have to call your bank or credit card company and have it removed or blocked, as with any other scam
To be fair, some Cruz supporters had the same problem, and that's what I told a few of them -- talk to your bank or credit card company. These automatic donations/charges can be a hassle to stop.. My newspaper delivery was like that. Canceled the paper, but continued to be charged. Finally went to the bank and the bank stopped the automatic deduction from my checking account.
I guess I'm old fashioned. Today I avoid those automatoc charge schemes anxd just send a check by snail mail. Don't have to worry bout being ripped off.