Forwarding the spam text to 7726 is an exercise in futility because the phone numbers are phony (spoofed). Verizon apparently has no way to identify spam texts and do anything useful about them. I've heard that AT&T does a much better job of stopping spam.
We are sorry to read that you are having issues with spam text messages, and we are here to help. Are you getting any error messages when trying to send the texts to 7726?