mortgage refinancing question

[Amir K.]

hello everyone,

3 years ago i took a $153,000 mortgage for 4.5% interest rate which was bought by one of the big banks about a year later.

now that same bank is offering me to refinance my mortgage for 3.5% and $2200 closing costs that will be added to the total sum and $395 application fee upfront.

now, looking at the numbers, it make scene for me to go for it, but why would the bank offer me this deal if im already paying them 4.5%.

sounds too good to be true, where is the catch?

thanks in advance