Phone is rejecting all calls (except one from a call center wanting money)

[Android Central Question]

I bought my wife a used rooted Galaxy S5. I put her SIM in and almost everything seems to be working. Except if we try to make or receive calls, the phone hangs up the moment the connection is made. I used it to call my own phone and my phone just BEEPs and says i missed the call. Her phone says the call was cancelled.
HOWEVER, It rang this morning and it was a charity call center. I talked to the guy long enough to find out they wanted money and I hung up. The phone worked for that. But I can't even call that number back.
I've checked all the block settings I can find. Any ideas??

 

[D Perich]

Additional information....

If I go into Settings/Network Connections/Advanced Calling, I noticed that "HD Voice and Video Call" was switched on.
I switched it off and calls no longer disconnect as soon as a connection is made but calls are still silent. No sound in either direction.