changing the price ot the rent by more than40% (Muscat)

my friend was staying in the same campus since Protected content months ago the owner rised the rent by 25% , my friend accepted the revised amount of the rent and now he received a three months notice to leave the villa because the prices went up and saying that he is not paying the same amount of the new people who just arrived.There are some villas empty till today because of high price of the rent.my question is :does he has the right to cancel the first contract and make him sign a new one
thanks for your help
Redha