Does the monthly cost of the iPhone Upgrade Program drop if I trade my current iPhone in?

I can't work out what happens if I trade my current phone in.

Do I just get all the money in one go or does it reduce the monthly cost of the upgrade program?

It could vary from company to company, you need to ask them.

You don't trade in your current phone not on the plan unless it's a phone already on the Apple upgrade plan. If you want to trade in a phone you can't use the upgrade program.