I sent a cancel email to DJI and got a message saying they can't respond because too many messages...so how the heck do you cancel?
I cancelled my P4P+ in favor of the P4P. The only way to do it is to go on their chat...and wait. It is the worst system on the planet. You'll see your number in line drop to single digits and then jump back up to the end of the line. That'll happen over and over again until you give up and then you'll magically hear the chime and realize you are on with them. They'll double check you want to cancel and then will do so. I got payment back within hours.