Yikes. I had a problem with a collection agency too, but that was not my fault, and after filing a complaint with SKMM/MCMC the issue has been resolved...relatively.

1) You made those calls, and you don't want to pay the bills? I mean, how the hell do you think you're gonna survive? Keep changing numbers every few months? So yeah, the collection agency is authorised to bug and hound you every day until you pay Maxis. They can't do anything more UNTIL they can prove you are "dengan sengaja" evading their efforts. Then, if Maxis authorises legal action, good luck.

2)Maxis won't cancel your subscription until you TERMINATE your account by paying your arrears and then cancelling.

3) Not sure.

4) Just pay. Make a civilised attempt at being responsible, discuss with Maxis and the Collection Agency on some installment arrangement, take a personal loan, cry to parents if you have to.