Been there done that,had bats in the attic for years,tried everything to get rid of them,they even got in the house 4 or 5 times during summer months.
Finally when I had my new furnace and water heater put in,I got the kind where it could be vented though the wall not the chimney,so I didnt need the chimney anymore,that is where they was getting in,so I had the chimney cut down below the roof line and sealed up the hole when I had a new roof put on.
Since then no more bats. .
The chimney was in bad shape so it was no loss. .