The way to avoid anything of this nature with MS, is not to talk to them. Laughing.
I avoid as long as I can. I do mostly everything online and when I have to phone them, a few too many pull up and make comments on other reservations - things that I don't point out, don't ask about and frankly are none of their concern (nothing against rules and a few do think they are being helpful.). Drives me bonkers.
Even then to deal with them directly, I try to email my needs. Don't forget that option with your situation.
I have also found that front desks have done things in this nature for me, without hesitation. Where MS was making a bigger deal about it. And most of the time there are very pertinent reasons that I needed this option.
There are some fantastic MS CMs for sure, lots. But a few too many get into your business, in my opinion. And some that have the most insane erroneous information. I had one *manager* that told me that I could 100% lose a NYE reservation if he tried to link it. And that is was only fair to other members if they grabbed it, for them to have the potential, about a month out. I still laugh hysterically thinking about that flow of insane communication.
Sorry that I used your thread to vent.
Good luck with everything. Have a lovely vacation.