Using one sandbox payment user for multiple publishers

Hey,

Currently we have few separate App Store vendors that we're developing apps for and the problem that we're facing is payment testing with sandbox user.

Apple doesn't allow to create sandbox user with email that has been used for sandbox testing for other vendor. Is there any kind of solution to ease up our QA process - switching sandbox payment accounts between every QA testing lane doesn't seem very efficient and not even remotely close to what I'd call convenient.

Creating emails with +1 is advised, but then sign up form results with an error.

Thanks!