I know EXACTLY what caused this issue to start for ME...TapJoy.
The calls--and TONS of spam-mail, EVERY SINGLE DAY--began IMMEDIATELY after I downloaded and installed an Android game made by a design team from my hometown in KY, and foolishly used the 'TapJoy' links in the game to try and get additional game $$ instead of paying for them...one of the 'Offers' was using the Burger King logo, and said something about getting a free meal (used the logo, but didn't mention the name, should've been a red flag, but I'd been sick), in exchange for 'Completing a Survey'.
I've NEVER been so foolish...the link took me to the LONGEST, most protracted, never-ending SET of surveys, all from different companies, many with different types of input, different-looking web pages, on my phone, and I really did (can't believe I did this), give them my email AND phone (retarded), after which the emails began slamming in my gmail account at a rate of more than six a day (dammit).  At the same time, the phone calls began, and since I didn't recognize the numbers, I realized pretty quickly that it was all due to that survey I took.
NOT worth it, of course.  This is my ONLY cell # right now, and the email I used (idiot!) was my PRIMARY gmail account.
SO...
As far as dealing with the phone calls, I've said it a dozen times here on 800notes, in order to help people out, so here's what you do:
Use the FREE, SAFE, call-screening tool called Youmail.  Go to Youmail.com, open an account, download it to your phone...everything.  Figure out how to block numbers--Youmail calls it 'ditching', and it even prevents these spammers from even leaving you VMs...
FURTHERMORE, here's what I do:
Since you can set a different incoming message for EACH person who calls you after you start using Youmail, I 'ditch' each and every number being used by these law-breakers (I'm on the no-call list for more than a decade, believe me, they're breaking the law no matter what anyone else tries to convince you).  THEN I set one of two Youmail 'custom' incoming VM's that are my long-time favorites for dealing with these...'people': one of the incoming VM's is just the old ATT "You have reached a number that has been disconnected, please hang up and try again".
Wanna see how fast these jerks remove you from their calling lists?  USE THAT ONE--any phone-spammers 'worth their BS' will routinely poll their number lists for numbers that are not being used, and so, wasting their 'precious time' (even robo-callers! again, this has worked for me for YEARS now).
My 'other' favorite custom incoming VM (almost ALL are absolutely FREE from the Youmail community, many comic, old cartoons, etc.) has been the one someone uploaded, and named 'Ear-Splitting High Pitched Whistle', which is my favorite because it's not a whistle at all, but instead, an audio oscilloscope test of some kind, and it's a doozie (starts out silent, then reaches noise levels that will bust an eardrum, then starts again...hilarious justice!).
So--do this, and you'll be happy.
Listen to any one of the jerks trolling this very site to 'one-up' me, and LIE to you, because they're obviously faking some kind of relationship to the actual FTC, etc., and you WON'T be happy--you'll be fooled.
Spread the word...again, Youmail is FREE--has been for YEARS, and I've run it without issue for that long (almost 4 years now), before I even started using custom ROMs for my rooted phone that will allow you to set your phone to silently process these spammers to the trash, as well (SlimKat's what I'm using now, but this is a whole 'nother story, as they say).
ENJOY YOUR PEACE OF MIND!