Bad management of the money

Every month the money I receive from them differs which I cannot understand because the Tennant pays a fixed amount and is liable for water and electricity. When you ask why I do not get a fixed amount in my account they are full of excuses and story's this is getting really old.as I feel they are \ *****ing "my money.I have been with Global Estates since April 2015 and not one month has there been a constant amount paid into my account.Now I am tired of this nonsense"""