If you need to take payments from people using mobiles there are many options available. One of the simplest is to use PayPal but this is not always an option depending on what type of business you are in or where you are located.
Essentially you need to be able to process credit or debit card payments and because this is such a basic business need, there are many solutions.
Apple Pay
Square
Google Pay
Amazon Pay
are all good options to check out although the app that is best for your own business will depend amongst other things on how much your products or services cost: if you charge a lot, you don’t want to pay a large percentage as a transaction fee.