Facetime/video call not functioning for most contacts on iPhone

video call not functioning on most of my contacts, it does function for a very few selected contacts, I have change IP addresses, I have discussed this with the genius bar (genius bar? FALSE advertising no one appears to be a genius there). It's like my mobile has been hacked, which I brought to both my providers attention on several occasions and Apples. I've been paying for a service that cannot use, it doesn't function as it should. POOR customer service all round. I do not want to speak to an AI or BOT or be put on hold several times over and over again with my issue not rectified. I want one on one personal service in the store. I do not want to have to make an appointment via email, website or text as hacking is too likely. I want a paper bill with customer service in store. One unhappy customer and i have been with optus for over 20 years. BAD form, BAD service, greedy company!

[Re-Titled by Moderator]

Original Title: facetime/video call not functioning