Can a mortgage company you where sold to change terms of your mortgage?

A mortgage and the attendant documents is a contract between you and your lender. When a lender sells the mortgage and notes, or the servicing rights to those, the buyer is buying your contract AS It IS. They do not have the right to change its terms. HOWEVER, you need to review your mortgage and promissory note VERY CAREFULLY. There may be terms in those documents that allow the lender or their assignee to invoke certain conditions in the mortgage or note that are adverse to you. For instance, if you are late 1 or more times in your payment, there could be a clause that triggers a higher interest rate or even accelerate the mortgage/note so you are required to pay it off.