Here are a few mobile phone and internet service providers in Hong Kong:
No contract SIMS- useful in the first few days of arrival although some may take 24 hrs to activate.
Birdie - They provide no contract options and SIM cards can be collected from various Circle K stores around Hong Kong and in the bus station in Discovery Bay. Requires the BIRDIE app. "No need to show up, no proof of address required, available 24 hours a day, supporting 180-day transfer reservations! Automatic renewal, no need to add value/renew, no contract means flexibility!"
SoSIM - Approx 33HKD They provide no contract options and SIM cards can be collected from FUSION supermarkets and Watsons Pharmacies.
Contract SIMS and Internet Service Providers- require HKID/ Passport. Before signing up double check coverage is possible in your apartment building especially if signing up for a combined package of phone and internet, especially in Discoverfy Bay.
3 - also offer family share (2 SIM cards share data)
Be prepared to allocate an hour for contract set up. Most stores have someone who can speak English to explain the contract commitments.