If you are getting calls from people saying you called them and asking why or being mad at you for making spam calls to their phone, most likely your phone was not hacked.
Spammers (which I am including vishers as part) can spoof what number that phone calls come from. These are calls that tell you that you have a credit problem, extended car warranties, medical insurance deals, etc. They usually have just picked a local number to appear call come from and on caller ID the spoofed number appears. Ironically, they use the spoofed number to call itself sometimes. For instance, I have gotten these calls and it shows my number as from. When people call you asking why you called or mad about spam, they will not understand spoofing.
There are a few times where the phone is hacked, and the calls are placed through your phone. This is easy to determine by looking at your phone log and see if there are outgoing calls you do not recognize.
Congress and the FCC and the FTC and phone companies supposedly have ways to stop these spoofed calls (and most spam calls) and are working on it. Up until very recently it was illegal to make the spoofed calls from within the USA to USA, but they had never made illegal to do the calls from out of the USA to the USA. That should help in enforcement. In addition, there are to be technical tools used in near future to block all these. The major point not enabling those laws now is how long to allow the phone companies to implement the technology before it is enforced that they must. Most if not all of us (except the spammers) would just as soon it be mandatory enforced starting last week.
Hopefully this is a problem they will successfully combat and, in a few years, someone finding this article will not understand what the problem was.