If I'm interpreting your question correctly, you're looking to set up a database of customers and include phone numbers. That part is pretty simple. All you'd have to do is create a table and include phone number fields.
The more involved part involves the phone calls. You'll need to buy a system that will read from a database and then make the actual phone calls. Depending on your location, you need to consider VOIP versus traditional phone systems, as they're handled differently. You should also consider whether the system you purchase needs to have recording capability.
If, on the other hand, you want to write a system to make the calls, I have no advice to offer. I've never researched it or even thought about it much.