Build a retail customer loyalty program

We're interested in starting a customer loyalty program for a small retail business. We'd like to build a system where customers could enter their phone numbers, emails, & name to sign up for a loyalty program. Then at our counter, they could enter their phone numbers when they make a purchase to earn points on their purchases. Ideally, we would also be able to use this information to track spending/trends, etc. We would also like to be able to leverage this system to send out phone number & email marketing messages periodically.

There are multiple companies out there offering these services for monthly fees, but we're searching to see if there a feasible option to create a system of our own, that we would pay for & maintain ourselves.