Banco Popular de Puerto Rico Mortgage Complaint

Banco Popular de Puerto Rico Mortgage department,

Conventional fixed mortgage Loan modification,collection,foreclosure Puerto Rico

I purchased an apartment 7 years ago and I got a ballon mortgage. My mortgage was for $180000.00 USD. Now I want to refinance my mortgage and the bank told me that I can not do that because now my apartment cost a lot less that when I bought it. I called the bank to request a mortgage modification, and they told me that the modification will affect my credit because, even though the account is up to date, that arrangement was not accorded when I first took the mortgage. What are my options? Is that even legal?