No, as long as one is a member of the telegram group/channel, you'll see the ads when it's posted or pinned by the owner/admin of the TG channel. You can obviously leave the group to block the ads permanently though .
It does and doesn't on the basis of what you want to advertise and how much you want to spend, if you want to advertise something not too important with a small amount, then trying out TG channels may be OK, but if your ads are significant, you have to top your budget and seek better platforms for your ad.