How to ask the same frustrating question without getting frustrated myself
At my job, I have to ask people for their contact information for what feels like a second time to them. Before they arrive, they enter their info online, and then I have to ask for it to enter into a different system. This system is the important one, which we pull from to notify them if they need to come back and repeat any testing - the one they used first is just for recruiting (the phone calls they DON'T want).
I've tried starting with "looks like we don't have a phone number in THIS system," clarifying "there are 2 different systems, this one is for test results," and even the full shpiel I gave in the first paragraph. No matter what, people get mad because "you already have it." I have to do 5-20 of these interactions a day, and it's genuinely a surprise when I don't get pushback. So you can see how that might start to get to a person, but obviously I can't fly off the handle/show that I'm irritated. It starts creeping into my tone by the end of the day though.
How can I handle this more gracefully? Part of the problem is that they usually don't want the recruiting phone calls they already signed up for. But I HAVE TO ask for their info, it's part of the procedure I'm following. I also can't tell who's first time and who's returning for the 100th time, so if I try to just start with "so we have 2 different systems and..." a lot of the time I'll just get cut off by people saying "yeah yeah I know, I'm still not giving you my number again." Which does make me mad.
Im starting to wonder if I have some anger issues to work on. But I have a lot of different instances of this scenario in my day-to-day (with different questions) and people generally act annoyed/inconvenienced by the whole process even though they chose to be here (this is for blood donation.) I don't want to be mean/rude/hurtful in any way, I just want to communicate the necessary info to get a response (and no is a response they can give, but "you already have it" isn't. Hence my clarifications) while following the procedure I'm legally obligated to follow. How can I frame this differently and/or keep my cool? I definitely care too much.