Dual SIM and separate Voice and Data

This may sound a bit greedy, but what I'd LIKE to do with my iPhone 11 and Dual SIM is set up separate voice and data accounts.

Specifically, I find Sprint works best for me for voice and T-Mobile for data. So I'd like to have the phone use only T-Mobile for data. I have a Sprint (Tello) physical SIM with an account that allows only a small amount of data and a T-Mobile account on the eSIM. I have set Sprint as the default voice line and T-Mobile as the cellular data line. The problem is that if I turn "Cellular Data Switching" on then I have no control over when each data line is used so that I might run out of data on my Sprint account; if I DON'T set "Cellular Data Switching" on then when I make a call on Sprint I won't get VoLTE (which is absolutely required).

Perhaps I'm asking for something that is THEORETICALLY impossible, I'm not sure, maybe someone can give their view. Essentially what I want (because only I matter :) ) is for the iPhone to use the cellular Sprint data ONLY for VoLTE.

Thanks in advance for opinions and/or pointers to resources.