if landed then will not use back existing phone port, need to install new cable and may need to drill hole but sometime not necessary you have to work out with the technician visit your place

if high rise building then have to use back existing phone port, will not drill anything or install new cable

landed can keep existing phone number at 0 cost (no monthly rental for this number unless you use it to call out then will be charge normal rate as usual) and unifi give u one more phone number (VOIP)

high rise will have to surrender existing phone number and you only have new phone number (VOIP)