Most telco plans (Celcom, Maxis, and newer DiGi plans) they are charging you by 30-seconds block.

So meaning to say, that if you only call your friend telling him that you have arrived at the meeting point will usually use like 5-10 seconds of call time - which you will be charged at 30seconds rate (since you've already use 1 block). This also applies if you only talk to 31 seconds (you will have to pay for 1 minute of talk time, since you're already using 2 blocks).

With umobile, right now they charge you by the seconds. So if you use 5 sec, then you only pay 5 seconds