Monthly Payment decrease when making large payment to principle

[David Keys]

So I have had many properties that I had put the typical 20% or 30% down on a 30 Year loan and had a Fixed payment with the bank.  When I had extra money or a large commission I would always put large amounts to the principle.  Is there a loan product that will adjust down your payment as you pay down the loan?  My payment always stayed the same even down to the last penny.  I know a company in Houston that advertises this, but I had a bad experience with them and wont use them again.  This would be a very popular program.  Wells Fargo has done 90% of all my loans.  They do not have this product.