Doesn’t matter TPAC, TATL, domestic, etc. A lap infant sits on your lap. If you want to protect your kid with a seatbelt pay for a seat and put them in a car seat or use another approved child restraint device.

Regardless, a crew member should have briefed you on travelling with an infant without having to press the call button.

EDIT: I see that Transport Canada specifically disallows the use of “belly” or “loop” belts as they say it is more likely to harm a child.

https://travel.gc.ca/travelling/chil...ren-on-a-plane