See the following articles that details this matter, especially the part on subject to:
There are several issues.
First, interest rates. I had a very old mortgage, from 1994, on a rental I own which I recently paid off. It didn’t pay for me to refi but the interest rate on it was 7.5%. You can see that these days it doesn’t pay for the bank to call the note.
Besides, this note was long ago sold to investors, which my mortgage was. Most mortgages these days are. I know this because it has a ID# associated with this mortgage for an investor when I go online to check on the mortgage.
Now technically, such mortgages can be called by the bank if they find out the property changed hands. In this case, they don’t even own the mortgage, and why would the investor, or even the bank, care if he’s happily collecting 7.5% with current mortgages at 3%.
Second, in addition to the above, there’s legal challenges to banks trying to enforce mortgage provisions when mortgages are sold, even if they try, see:
So issues when loans are being called are, it doesn’t pay, and they can’t…