Word for former/previous user (someone that stopped using something)

Question

I’m looking for a word to describe someone that used to use an app/service, but doesn’t anymore.

Surely, there must already be a word used in marketing to describe this concept.

Example of usage:

“We need to create a marketing campaign to win-back all of our [users who used to use the app/service but do not anymore].”

Answer 1

1. Former users
2. Inactive users
3. Lapsed users