Issues making some home landline calls

[emiliamariani]

Having issues making calls to particular home landline numbers. I can recieve calls from these numbers but get an engaged tone every time i dial these particular numbers.
Help please as the number in question that I can't get through is my son and i am dependant on him.
His phone can recieve calls from other people just not me.

[PeterW]

Hello emiliamariani,
Thank you for being a part of the TPG Community.
For verification purposes can you please send me a private message (PM) by clicking on my name and provide the following information:
 Username
 Full Name
 Full Address
 D.O.B.
I will reply ASAP on receipt of the above.
Regards
PeterW
My TPG app for IOS and Android - https://www.tpg.com.au/download