Three ways. 


1. Customer can simply click on the unsubscribe link provided in the footer of each sms they receive.

2. A customer can be unsubscribed in the store by the staff on the Clover station.

3. A customer can be unsubscribed from the UMarket->CUSTOMERS-> any customer listing.

 

Either way, the customer will cease to receive your promotions.


Please also see different UMarket Marketing Settings.