Apple ID was damaged. Do I lose all of my content and have to wipe my devices?

I have an iPhone 6s and Macbook Pro 13" (High Sierra) retina. I updated my OS on the phone and got locked out of my Apple ID unexpectedly. Two weeks of telephone support later - my Apple ID is inaccessible by Support and I was told to create a new Apple ID. All of my content stored and backups on iCloud and in iTunes/Movies will be lost as the old ID was associated with all of my content (apparently, because the account was so old(?) - I've been a Mac owner since the early 90's). Top Apple support tell me they can't do anything and all of my content is toast. I didn't think this could be possible working in the Cloud...?

I can't create a new ID on the phone because I have to login first to disable, and can't change/update my old ID online because it doesn't exist.

My question, now that I'm recovering from a heart attack: I've created a new Apple ID on my computer, but can't link it to my iphone. Do I have to hard wipe my iphone and start all over again with my new ID? If this is the case, is there any way to try and save anything on my phone before wiping it out?