I started a call answering service for small to mid businesses struggling to get first clients. Any advice?

Hey everyone, I recently started a call answering and BPO company targeting small businesses in the US. We handle live phone answering, appointment scheduling and lead capture for business owners who can’t always answer their phones.

I’ve been doing cold email outreach and posting in Facebook groups but haven’t landed a first client yet. Has anyone here successfully marketed a service like this? What worked for you?

Any advice appreciated.