Rebshiduch,
Where do things stand? Are you going to speak once more on the phone to say good bye?
If it was me
I’d start by respecting their decision
I would thank the person for learning with me because of how much I gained from the experience (new insight to my own Judaism, thinking about great questions they rose).
I’d ask for feedback on what they found most interesting/enjoyable from the learning.
I’d ask if they were to consider continuing or restarting what time would they see working best and topic they’d find most interesting.
Of course I’d talk to the group who sponsors the learning.
A guy I know told someone not frum a hashkafa vort and the guy got interested in learning. I was set up with the person to learn through an organization and told that “gemara works better than hashkafa” so we learned brachas for a few weeks and the guy really was uninterested and dropped. In hindsight I would have learned fascinating hashkafa with him. The truth is that would have been a lot more work for me at that time but it would have worked I believe. There may be packets made by smart organizations for kiruv. I recently participated in a one night session through Ohr Sameach and they had a fascinating packet. Wasn’t hashkafa but it was done top notch intellectually for college kids. It traced the gemara about yaharog vaal yaavor to questions like abortion, when to give over a person in a city etc.
Hatzlacha in your kiruv.