I found this and I think some of them are hilarious xD

Prank Call Idea #1
This is an oldie and I have been the victim for the same!
You call up the person and ask for a person name Joey. Since there really is no Joey, the obvious answer would be, ‘You’ve got the wrong number’! Call up the person many times during the araw or week and disguise your voice in varied accents and ask for Joey. After a few days, call up your victim and say, ‘This is Joey. Have you taken any messages for me?’ I am sure the person at the end of the line would probably want to strangle you with the telephone wire because I had wished to do the same!

Prank Call Idea #2
Call up the local Chinese eat out and insist on ordering some American fast pagkain and why they should include it in the menu! Throw a tantrum!

Prank Call Idea #3
Here’s another funny and irritating prank call idea. The conversation should go as follows. The person who picks up the line would obviously say-
‘Hello’
You: ‘Hello?’
‘Yes?’
You: ‘How may I help you, Sir?’
‘Excuse me, you are the one who just called me!’
You: ‘Sorry sir, but you have just called me.’
‘No, you are the one who has called me.’
You: ‘You’d better reveal name or else I will have to hang up’
The person may hang up and you can also do the needful.

You can call the same person up after some time and say-
You: ‘It’s you again! I would have to ulat you to the cops!’ This is bound to leave your caller exasperated and clueless about what is going on!

Prank Call Idea #4
You call up your victim and pretend to be an engineer from the phone service. Say that the phone lines have been giving some problem and you would like to test the voice quality. Select a few stupid phrases and make your victim repeat the same for voice testing!

Prank Call Idea #5
Call up your victim and pretend to be an DJ from the local radio station. Say the recording is being played live and ask your victim to answer three tanong to win a weekend trip to a happening destination. Make a listahan of naughty or funny tanong and embarrass him/her!

Prank Call Idea #6
Call up your victim and pretend your call is from a website that has confirmed the bookings ordered sa pamamagitan ng the sinabi person. The person is bound to object to any such order, you can argue and insist for the remainder payment for the sinabi number of goods! And insist upon the delivering the same immediately.