Some Christian groups take these instructions literally. For example Jehovah Witnesses consider visiting people in their homes and talking them over a core part of their believes.

https://ar.wikipedia.org/wiki/شهود_يهوه
يتميز الشهود بروابطهم المتينة دون أية حواجز عرقية أو قومية، ووعظهم التبشيري الدؤوب في الذهاب إلى أصحاب البيوت وعرض دروس بيتية مجانية في الكتاب المقدس

https://wol.jw.org/ar/wol/d/r39/lp-a/1991044
ان شهود يهوه معروفون جيدا بخدمتهم الفعَّالة من بيت الى بيت.‏ ولكن لماذا يذهبون من بيت الى بيت؟‏

Witnessing is telling others about the forgiveness, love, deliverance, empowering, fruitful life and ministry, etc., that you have found in Jesus

I will not quibble over the translation of the word "witnessing" here, whether it is شهادة or تبشـير. I will, however, address the meaning of "witnessing." You probably already know that ordinary, everyday witnessing is what the faithful spontaneously say and do as they go through life, which others observe and take as a testimony of their faith, hence the word "witnessing." However, witnessing can also be pre-planned evangelical activity for proselytism. To call that kind of activity "witnessing," properly speaking, it must be personal and experiential, not memorized formulaic evangelism. However, the two concepts are often not clearly distinguished, so the terms for witnessing and evangelizing are often interchanged. But you already know that.

What I want to address mainly is the expression "door-to-door" used as an adjectival modifier to "witnessing." Where I live, I occasionally receive door calls from all kinds of cheery-faced evangelists (usually in twos and threes) who say a few words about God's redemptive plan and then hand me a little pamphlet, which usually ends up in the recycling bin. On rare occasions, they come in, have some Lipton tea, and do more witnessing. These (typically young) evangelists hit people in their homes, not businesses, because businesses do not allow such activities. Therefore, it is legitimate to say بيتاً بعد بيت instead of a more literal rendition.

I think, however, that doors are important to mention. The whole affair seems to occur at the door of the apartment or house they visit. Many of them have strict instructions not to enter anybody's home due to security concerns. Also, most people would not allow strangers into their homes, regardless of their angelic faces and sweet words. And when nobody answers the doorbell, they usually leave their evangelical goods at the door.

For this reason, I choose the expression طرق الأبواب بيتاً بعد بيت

In this particular context, however, I would recommend simply طرق الأبواب, mainly because the reader (the poor little evangelist who is refusing to participate) already knows the serial nature of the activity. Here is how I would render the whole sentence:

By ... refusing to do door-to-door witnessing, you are
إنكم بامتناعكم عن طرق الأبواب للشهادة

If you feel you must include بيتاً بعد بيت, I would not fault you.

Finally, I must say a word about the the group that authored the material you are translating. It is clear to me from their fear-based approach ("you are indirectly assigning people to Hell") that this is a pernicious, exploitative group. I personally would not provide any translation services to them. I will, however, continue to help you with your terminology questions that you post here because that is for your linguistic development.