In addition to the special forbearance relief afforded by §§ 203.340 through 203.342, if the mortgagor is a person in the military service (as defined in the Soldiers' and Sailors' Civil Relief Act of 1940), the mortgagee may, by written agreement with the mortgagor, postpone for the period of military service and three months thereafter any part of the monthly payment which represents amortization of principal. The agreement shall contain a provision for the resumption of monthly payments after such period in amounts which will completely amortize the mortgage debt within the maturity as provided in the original mortgage. The agreement shall in no way affect the amount of the annual MIP which will continue to be calculated in accordance with the original amortization provisions of the mortgage.