Credit system or limited by minutes?

Hey y'all, I have a tool for Sales teams to help getting new reps comfortable on calls in a week instead of 4. Basically it's a tool where you roleplay sales calls with AI prospects who push back, and get feedback and advice after every call. I have got a good amount of testers from LinkedIn who have given positive feedback.

I currently have a free plan + 2 prices. €14,99 and €29,99.
However I'm thinking of deleting the €14,99 price fully because it only has text-to-speech calls and they are low-key bad quality.

But at the same time I'm thinking of adding a credit system, because the AI costs me too, and it would honestly make sense for calls.

What do you guys think? Credit based or limited by minutes a day?