Installment issues with my new salary account

I got a loan from Fast Solution when I was working with Shell. When I got a new job in March, I sent an email saying that I had switched my salary account, but you still tried to debit my old account, which is bouncing. I sent an email asking them to address this, and I learned that I needed to go and certify an affidavit. My job does not give me time off, being a nursing mother. I am struggling to get the affidavit. I am worried because I am two months behind on my installment.