My house roof is leaking during raining day.

Suspect is due to loosen roof tiles.

Any contractor to recommend ?

If you dare, just climb up the roof and try to spot which one is the culprit.
Go to hardware shop buy those asbestos glue, tell them it's for roofing, and they'll recommend you.

Once you found the spot, if you do indeed find it; shift the tiles and fill/plaster that leaking hole.

My roof is leaking as well and happens only after raining. How much will it usually cost to repair the leakage?

It's still advisable to check ownself see whether or not it's tile cracked, tiles out of place or a hole in the roof. That's to prevent from being conned by contractors also.

But sorry, can't help much in "contacts" though. Good luck.