Bail

Yes what is the problem in that.

Yes he can buy. There is no restriction on accused as well as on convicts to use any sim or mobile phone if they are out bail. 

I mean a new sim with the old (existing) number.

Mobile phones are not only used for communication but nowadays they've also become a way of living nowadays as mostly everything is socialised with the help of internet.

A person accused of an offence though been released on Bail is all set to live a normal life, and since usage of gadgets is one of them, they're involved in the use too. However, it is expected from a person released on bail to prohibit any action, activity and even involvement in any such activity or action, which can cause him or any people trouble.

In general, the person on bail is expected to lead a life as a Law Abiding Citizen and avoid in activity performance of which is prohibited in law.

Hope it helps.

Thanks