iphone 6 “searching” or “no service” after housing change

so i purchased a iphone off kijiji but the phone has no service
it says no service but if i reset network settings it says searching
ive checked all the screws (including the two antennas on the top left of iPhone) and they are okay im going to replace the bottom lightning assembly soon maybe thats the issue because it has the antenna built in ?
but i dont think that the issue but haven’t done that repair yet reason is
that in settings all info is available like modem firmware and imei BUT when i click *#06# nothing happens the screen doesn’t even go grey but the screen doesn’t freeze either, no info on imei what should i do?

ive read that i should reball the Power Supply IC PM8019 Chip i have all the equipment but im intermediate so would like to know all my options before ( what temp would i reball at? so remove ic and also heat solder past at with stencil )

what about re flow ? (re flow at what temperature with air gun and at what fan speed ) that just like heating the ic up till the solders liquefy then solidify making a good solder?

ive read previous threads on this but not enough info

and or any other options ?