These scammers changed their Caller ID name from SNR ASSIST to CLIENT SERVICES. Why? They're still crooks. A POS by any other name would smell as crappy.
Call the number back and you will hear, "If you would like to be placed on our Do Not Call list, please press 1 now." After pressing 1, "It may take up to 24 hours to process your request." I wonder if this will work?