What will happen if I can't pay my (OPTUS) handset bill?

Generally a phone company will block your number from making calls first , then disconnect altogether until you have paid the bill. If you are on a contract they may disconnect and then charge you a fee for terminating your contract early.

It is best to ring them and talk about an extension or other options for your bill.

I'm surprise that you electricity have not been cut off for non payment.....The electric company will not track you down..Just will keep that balance of your account until you decide to renew services again. Then you will have to pay the outstanding balance plus penalty. They will also ask for a security deposit to start service, since you left them with a bill last time. The electric company only cares the account holder's name, not if you have a roommate or a friend that is responsible for the bill. On my experience, I have put the name of my roommate on my electric account, to make him/her responsible for the bill, so if either of you leave the other one will have the same fate as I explained above, if they want to activate service under their name. Keep on mind, that it will be reported to the Credit Bureau

My Optus Pay Bill

Then you'll die.