Who do you call a lot? (?)

Whom do you make often calls?
See Summary at https://writingexplained.org/who-vs-whom-difference
Whom are you calling? — just a basic sentence to start with

++++++++++Zoya! Very good, very natural!

Elena, your translation isn't quite correct for several reasons. (1) we make (phone) calls TO somebody. But regardless of that, it sounds more natural to just CALL SOMEBODY; (2) although WHOM is grammatically correct, it's extremely optional and rarely used in the modern world. We tend to avoid it in the everyday language because it sounds pedantic; so we just use WHO; (3) Russians use the word часто much more that English uses OFTEN. In the real world, in neutral contexts like this, we would use A LOT. The word OFTEN of course has it's place - usually when it's modified: too often, very often, quite often, but not usually on it's own.

Здорово!! Спасибо, Улий!))

👍🏼😉