I called back number (07) 3422 6795 rang once then goes to busy tone.

Called my 14yr old niece looking for me and I don’t even have her number to give out.

I called back number (07) 3422 6795 spoke to a guy who said company name is Credit Corp.

I called back number (07) 3422 6795 rang 5 time then goes to busy tone.

debt collectors

This person (Sam) called my elderly mother asking for information about my ex-husband who we have had no contact with for over 25 years. He tried to reassure her that he wasn't trying to sell her anything but that it was a personal matter and that the ex would know about it.
So Sam if you are legitimate and you have nothing to hide IDENTIFY YOURSELF and WHERE YOU ARE FROM. At least with display phones we can see the phone number you are calling from.
If you are really looking for the ex then use Google & Facebook. I found him in 10 seconds.

These guys rang me looking for someone else then proceeded to tell me that I must know the person in Question - I told him I didn't. then told me to pass on a message to the person he was looking for. "Come on mate you know him tell him to Call Sam with regards to a personal matter" Ok Sam where did you say you were from.. "I didn't he knows what it is about" I don't know this person but ok. "just pass on the message when you see him. bye"