How do I add Pylon to customer-created Slack channels?

If the customer created the Slack channel, you should be able to add Pylon into the channel as if it were your own provided you have the permissions to invite members/apps to the channel. Everything will work as intended.

What if I still can't add Pylon into the channel the customer created?

If you're unable to add Pylon as you normally would, this means your customer has set stricter channel permissions and you may need to ask the customer to give you permissions to invite users.

Here's what they'll need to do. In Channel settings, look for organization and select "Manage permissions"

Then change the permissions to "Post and invite"

You should be able to add Pylon in as well as other teammates.