Has my AT&T wireless account information been hacked?

My wireless account if fairly new - I just set it up with two DuraXE phones last summer.  At that time I logged into my wireless account online and specified the Caller ID names for each phone.

Recently, I have been receiving a large number of repeated calls from unknown and bogus phone numbers - I don't answer any of them because they are neither listed in the phone's contact list nor do I recognize the number.    The repeat calls must be coming from robo dialers because they'll show from a single number several times a day and go on for days.  

I was wondering why I was getting all these calls so I entered my cell number into a Google search and found that it was listed on a website by OKCaller.com - besides listing the number and location zip code, they also show my caller ID name that I had recently entered into the AT&T system.    I did the search on my second phone number and they also had the caller ID name for that phone also.

I called AT&T and asked if they were giving this information out to anyone and how this OKCaller.com website would have it.   The customer service rep said they don't give out wireless numbers and tried to convince me that someone at a businesses to whom I had given the number could have given it out.   That would be feasible except that my primary phone number is strictly private and has only been given to two family members.

So,  how did OKCaller.com get my personal ID names and other phone information?  Has my  AT&T wireless account been hacked?