Are these sentences written correctly?

Not sure if these are written correctly with comma. Also second sentence, can you start with unless?

Roy told me to let you and others know, not to leave your cell phones on the bleachers. Unless you want to go buy a new one.

[Jason72]

1. Omit the comma.
2. Starting that sentence with unless is fine, but it would be better like this:
Roy told me to let you and others know not to leave your cell phones on the bleachers, unless you want to go buy a new one.