Are the numbers calling you in the Nomo database? You can lookup numbers on their website.
One of the problems with Nomo is spammers will use an unreported number once. Meaning, nobody had previously reported the number to Nomo. If the process works as advertised, a subscriber receiving the call...such as you...will report the number to Nomo. If Nomo gets enough reports on the number, they'll add it to their block list. The next time the number calls you, Nomo will block it,
If you're receiving repeat calls from the number, either nobody has reported it or not enough subscribers have reported it. However, as I mentioned, the spammer are probably using a number once, switching to another unreported number and calling you again.
There are 10 billion numbers for spammers to spoof. Nomo can't block 'em all.