What are the books that establish a new Muslim in their faith and refute misconceptions, especially given that communication with them is only possible by phone or over the internet, and who is the appropriate person to provide this assistance?

Among the beneficial books on how to deal with new Muslims is: (Al-Mufīd fī al-Ta‘āmul ma‘a al-Muslim al-Jadīd) by Sheikh Muhammad Salih al-Munajjid. And among the useful websites is: Kalima Sawaa Islamic Network, which is concerned with refuting Christian misconceptions. The default for a Muslim is soundness, so there is no need to doubt his religion and methodology as long as he is with scholars whose apparent state is righteousness and uprightness, until proven otherwise.