Because of trade deficit that is already in China's favour. I assume banning these companies means further actions on China's part that will impact India even harder.

Would deficit reduce if we ban mobile providers, since deficit is more on side of India.

Doesn't china comparatively has lesser moves than india as it enjoys trade benefit far more than India.

No here we don't know what steps they would take, they could block trade of things we need. Its not just about the trade deficit itself.