how can they raise my mortgage after escrow closes?

yes they can change it. insurance and taxes are always estimated and always changing.

$300 seems a little high for a change but it could happen. Ask them why it changed. That is a valid question to ask. do not be shy.

Apparently your property taxes (and maybe homeowner insurance) is escrowed. That is not unusual the first time you get a mortgage and you should have been aware of it.

So $2400 is apparently your loan payment, and $300 is likely escrow, probably just for property taxes, since it seems quite reasonable for that high of a loan payment (my property tax is higher for much lower mortgage payments). Even with a fixed rate mortgage, your escrow can vary with property taxes.

If it is not escrow, and you did not put 20% down, maybe it is private mortgage insurance.

I agree with David. Once a mortgage is signed, the amounts of principal and interest to be paid monthly are not subject to change. However, any amounts required to be escrowed for taxes and insurance CAN be changed to suit the needs of money required to pay off such expenses.

You need to contact the lender to see why any such increase is being demanded. It is very possible that the annual property taxes were underestimated when you purchased, and now the lender wants a monthly increase to insure that you have sufficient funds in escrow to pay those taxes when due.

I am sure it has to due with actual insurance and property taxes, not estimated costs. Also do you have a fixed interest or a variable interest rate? That can make a huge difference in the long run of a mortgage loan. If they offered you a variable rate to get you into a loan and your interest rate has gone up since you signed the loan you make want to check out a fixed rate loan and refinance sometime in the future.