I bought a house few months ago, I already sign the papers for the new mortgage and pay what they told me to paid at the moment and the deal is close, and already sign, I got the keys and at the moment I am painting the house, today I got a call from the company I took the mortgage and they told me they have made a mistake and that know I should pay more money, or change to a fix interest.

It is there something I could do?

Call them back and tell them to send you something in writing that completely explains in detail why they think you owe them money. Wait and see what they send you. Don't send them any money based on just a phone call from them.

Assuming you closed and signed final mortgage paper work, and not some temp finance you are obligated to pay exactly what the loan papers say, so get your copy out and read it first of all.

Now it is not unheard of, to have an adjustable mortgage that resets ( some every few months, others every few years)

So how does your adjust

Good info so far. We really need more info on your mortgage. Are they saying it was a mistake or that your adjustable rate is changing?