Honoring Pre Approvals

I am a vet and went to Bof A for a home loan and was Pre Approved. I had a pre approval letter in hand and went home shopping with my realtor. We found a home and the owner accepted my offer but when we submitted the purchase contract they said I wasn't approved because of my credit. After speaking to the processor he told me I had collections on my credit. The problem is they had been on my credit when I was pre approved and they wanted them paid it could have beena an underwriting condition. I called my LO and left messages and he never called me or my realtor back. I submitted a complaint to Bank of america and never got a response from them, just a confirmation