Sorry, I dont understand.

You have a contract. Bank gives you X QAR with an interest of Y % to be paid monthly during N months.
Black and white, signed and stamped, isnt it?

They cannot charge you more unless there is something in the fine print of the contract (Bank reserves the right to change interest in case libor goes upper than... or something like this).

Please share your findings, Im really interested...

War looking for peace,
is like fornication looking for virginity.