You can use Twilio Voice and TwiML Pay to build an app that accepts mobile donations for your non-profit organization. To start, you'll need a free Twilio account, a Twilio phone number, and a pay connector (such as Stripe or Braintree) set up with your payment processor. You'll also need to enable PCI mode on your Twilio Voice settings. Then, create a Function service in the Twilio Console and build a function using Twilio Functions that responds to incoming calls by asking callers to enter a donation amount and then their credit card information. The function will use the TwiML <Gather> verb to collect the caller's input and make an HTTP request with the collected information to your payment processor. Once you've set up your pay connector, you can connect your Twilio phone number to your Function and deploy it to start accepting mobile donations.