Can i have those IPTV service who offer free trial before actual purchase of subscriptions ?
Any decent IPTV service provider will give you a test line for 24-48 hours. After all, you need to know what you are buying and the quality of the service. If they don't have a test period, it's better to look elsewhere.
When you do your testing, check if the picture lags and freezes in the evening hours when there are usually more viewers. If you are into sports, check the stability on channels that broadcast a derby, a match that will draw many viewers. If the performance isn't up to par, you either have a bad internet connection or the server is oversaturated and oversold.