Do i HAVE to file serperatly from my husband when dealing with income based student loan repayment?

I have student loan debt and have recently entered an income based repayment plan. I was informed by someone who does taxes that I could file a certain form and then file jointly with my husband and that would allow me to not include his income in my repayment plan. I was also told by an individual with the company that arranged my repayment that only filing separately would insure my husbands income wasn't taken into consideration. Help! Which is it?