If I paid my mortgage twice in a month is it still possible for the mortgage co. to apply it for next month?

I mistakenly double paid my mortgage twice for December--I didn't mean to do that. My purse was stollen together with my checks so I had to cancel the stolen checks. Yesterday I just got my new checking acct # and I thought the previous checking acct # wouldn't work anymore so I immediately supplied (online) my mortgage company the new checking # so I wouldn't be late for my payment but unfortunately the old checking acct # went thru plus my new acct # so when I check my balance--I was double billed for December. It says in the letter from my motrgage company that once paid--the money can not be returned. I am not gonna ask for a refund--but I hope they could at least apply it for my next months bill.