keeps calling every day and never leaves a message.  I have it blocked, but they sometimes call 3 or 4 times in a roll so it still rings for each time they call once.

Same here; calling my cell phone several times a day.  The truecaller software on my phone says "Tamela D. Traylor" and reports 16 spam reports, including mine.  Does not respond to a text advising wrong number, so assume it's a spoofed robocaller.  Annoying, as even if blocked you have to take the time to check.
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While that app might be named "True" I doubt it is any more reliable than asking an 8 ball who called.  The net is notorious wrong most of the time as to who actually called.  Further, since most scam numbers are spoofed you might be looking up the number of an innocent victim.

Debt collector

Yep... ironically, TXU kept calling my phone about a debt with a person that I suppose had my wireless number before me.  The recorded message says to call them to straighten it out if a wrong number, but I can't even understand the name of the person they're calling and have no information on the account, naturally.  Pretty frustrating when they turn it over to the robocallers who never get tired.