Who Is Looking At Your Phone Calls????

I'm telling you this is scarry!
You all know about my financial problems of late, Well we are wayyyy behind on our one and only credit card from Walmart. We know it, they know it, We have tried to make a few payments but they add on an over limit charge on top of the interest rate which makes it impossible to ever get to an affordable payment range...
Anyway, They call us constantly I'm guessing about 7 times a day, It is a message telling us to call them. I have stopped picking up the phone when they call (being that my phone is one of those pay as you go phones, I waste minutes every time I pick up). I was getting a little leery when right after I would talk on the phone they would call, making me feel like they are able to monitor my phone calls which is freaky. Here is the topper, They ARE scanning my calls and they saw what phone number I was calling and started calling that number!!!!! It happens to be my son's phone number of which I NEVER gave to Walmart on the credit card application. They are now calling him constantly thru out the day also. Isn't this really scarry how someone not even govt. related can tap into your phone calling! This has me pretty freaked out on many levels, I mean how many times do you give out your phone number???? I can think of endless number of times I have given it out and you never know what people are doing with it. Are these same people who are able to tap into your calling able to tap into your conversations????? They obviously know exactly when I'm on the phone and with who, maybe even the location I am calling from : ( My son called back the number and told them that he wants his number removed from their calling system immediately. It really is mind blowing and creepy!!