I foolishly upgrades my iPhone Xs to iOS 13 0n 9/23/19 and then my iMac desktop (running High Sierra) in iTunes wouldn't recognize the phone on my desktop, but the phone would show up in iTunes on my laptop (also running High Sierra), after 2 hours on the phone with various Apple (tier 3 representatives) I was told my only option was to upgrade the desktop to Mojave which would have the necessary "drivers" for the iMac to recognize the phone. I didn't want to upgrade to Mojave, because I now can't use some of my other applications. After loading Mojave and launching iTunes, then got another error saying I had to load additional software in order to recognize the phone, which I did and it recognized the phone. I synced the phone and all my contacts on the desktop and phone were duplicated. I manually deleted all the duplicate information in my contacts file on my desktop , launched iTunes and selected replace contact information on this iPhone with information from this computer. After syncing the contacts with my iPhone some contacts are duplicated some in triplicate. Then noticed there was a fix iOS13.1, downloaded this hoping it would fix it, but it did not. I manually count 1190 contacts on my iPhone, but only have 556 contacts in the contacts file on my desktop. Noticed today while waiting on phone with Apple there was another fix 13.1.1 downloaded that too, but it didn't fix the problem. I had also tried removing all contacts from my iPhone and tried to replace the contacts with those on my desktop and each time the same thing. Today I spoke with Apple support again and was told since iTunes is going away my only option is to store my contacts in iCloud. iTunes no longer accurately syncs my iPhone and my iMac since loading iOS13 and there is no fix as far as Apple is concerned. I was also told there is no way to go back to OS12 once you upgrade to OS13, because even a factor reset will default to iOS13.
