Subscription code not stacking - poor experience with customer services

I thought I'd take advantage of the Amazon sale and buy two 1TB Photography plan codes so that I was covered for the next 2 years (something I have successfully done in the past) however this time instead of stacking the second code created a separate membership.   No problem I thought, just a technical error so customer services should be able to sort that out easily - how wrong I was.

First I had to battle past the AI which really didn't want me to talk to a real person.  Once I finally got through the agent seemed to struggle to understand the issue - eventually they grasped the problem but couldn't do anything so they escalated it to a manager and assured me it would be fixed in 48hrs.

48hrs later still not fixed.  Battled past the AI again which insisted my case was closed.   Got through to an agent who also insisted the case was closed but after re-explaining everything again said they could cancel the extra membership which would have meant I would have lost my money.  After several minutes of back and forth the agent said he'd made a mistake and my case wasn't closed but was still waiting for a manager to look at it, please wait another 48hrs.  

Another 48hrs still nothing.   Battled the AI again.  Insisted to the agent repeatedly that I wanted to speak to a supervisor and they eventually relented and put me through to a supervisor.   
Had to go through most things again and was told the only resolution was to cancel the duplicate membership and they will issue me another code in 5-7 days (was told they can’t extend membership past a year).  So currently I'm out of my money with nothing to show for it and reliant on the not so reliable Adobe customer services to issue me another code in 5-7days time and I still don't know if it can be added to my existing membership. 

Looking through the reviews on Amazon I'm not the only one with this problem.

I’ve been a paying member for 10 years and while problems have occasionally occurred they’ve always been easily rectified.   I don’t understand how such a simple problem to fix has been made so frustratingly difficult and time consuming to resolve.