Rats are difficult to be rid of. Basically you want to find their run (their paths) and bait around there.

There is also bait you can chuck up into the roof. Iirc, they dehydrate the rats and they leave to find a water source. Be aware of you have pets though, as cats may catch the rat and get poisoned too, or dogs may eat the bait.

Other than that, trying to find where they’re getting in and closing it up. They’re notoriously difficult, but don’t leave food out or anything that would attract them.

A pest controller wouldn’t do much more than the above tbh, having worked for a pest control company.