Typically all lenders and service organizations do not deal with buyers directly. They hire a brokerage to sell the property directly. You can have your realtor contact the listing agent or you can call the listing agent directly if you don’t care about any representation. If you do call that listing agent that agent will get both sides so try to get a rebate out of him/her for some of the commission. If you list the property address I can let you know who is representing the property. If you don’t want to list the address of the property I understand.
Robyns Song and Bugs are absolutely right in thier posts. The servicing org will definitely want to do the BPO before they list it on the MLS and they will not look at any offers before that regardless.