People are always looking for new customers. That's really difficult to do and no-one enjoys it. Keep your customers happy and they will keep coming back to you. That's the easiest way to get more work. Once a customer trusts you they will use you again and again.
But they also need to be able to find you. We help with that.
If you need a paper invoice from 2 weeks ago can you find it? What about 2 months ago? It's the same problem for your customers.
When a customer needs more work done in a few months, maybe it's an emergency, they will use whoever they can find the quickest. They've probably lost your paper invoice. If they have an invoice in their email or WhatsApp they can find you...and they will call you.