all phone carriers have the same way of reporting sms spam ( in the united states) . please forward your message to 7728 (spells spam ) and follow the directions
copy and paste the text message to 7728
7728 is text based and won't accept screen captures, like apple iMessage wants
since the message came from "9766", you could also try sending a message saying STOP ALL to them.
maybe double check your phone bill to make sure this isn't a subscription service that crammed you
i heard if you send them HELP it might tell you who the short code belongs to, useful if you found your # got crammed with SMS fees