Sales people that want me to do their job for them

OK I was just trying to get your attention with that subject line:)

How do I respectfully say no to account executives that ask me to perform tasks that they should be performing themselves?

I'm 35 and have been in IT my entire career. For roughly the first half of my career I was doing billable consulting, and for the past 5 or 6 years I've been doing technical pre-sales whereby I support account executives in the field as the "technical expert" to help close opportunities. I'm a high C / High D. I've also spent some time personally owning a pipeline and quota. I completely understand and respect the high I behavior and this post is not at all meant to be derogatory towards high I's.

Our account executives own various processes, for example filling out an online form to request pre-sales technical resources. There is absolutely no ambiguity around the account executives ownership of this. My team has actually been given specific instructions by our leadership not to perform these tasks for the account executives. There's a reporting element involved that's the primary reason; if I complete certain processes on behalf of the account executives, then the paper trail doesn't track back correctly. But that doesn't stop the AE's from continuing to ask us anyway. :) But also, if my team starts doing this work for the AE's, then the AE's will obviously keep asking us to do it; which is why the technical organization has been given explicit instructions not to do this. We don't want, nor do we have time, to become data entry clerks for the AE's.

So when AE's ask and I push back, they'll continue to push back on me to do it. And once they realize that I simply am not going to do this work for them, they oftentimes will act as if I'm being uncooperative or not being a "team player".

Obviously this is classic high I behavior and I get that. And, I have many AE's that I support and I simply cannot do this work for all of them anytime and everytime they ask (nor should I). I've tried various "excuses" such as "I'm travelling this week", etc. But those are short-lived excuses and don't prevent AE's from attempting to delegate their work to me the following week. So ideally what I need is a way to definitively set the expectation that I'm simply not going to do this work, without giving the impression that I'm difficult to work with. I don't hold it against them that they're asking me to do this, because I understand the high I behavior, but at the same time, I don't want them to hold it against me that I WON'T do this. Any ideas for how I can accomplish this?

Jason