My terms are as follows:

4.940% interest rate
$18375 balance. (Original balance was $22000)
$154.75 payment per month

They changed me to an "interest only" loan basis. If this was the case the payment calculates to around $74.60 per month. I do not understand what they are doing and they will not explain what they are doing. Every payment I make of $154.75 makes my principal balance decrease by $0. Can anyone make sense of this for me?