Purchasing an "unlocked" phone from a manufacturer or retailer like Best Buy is the most flexible option. This allows the recipient to simply swap in their current SIM card or activate it on their own plan without you needing their account details.
The most effective way to gift a phone is often determined by the recipient's existing service setup: can i buy a phone for someone else
If you share a plan with the recipient, you may be able to use their "upgrade" eligibility. However, this often requires you to be an authorized user on the account and may trigger a new service contract. Critical Considerations Purchasing an "unlocked" phone from a manufacturer or
How to give a phone as a gift this holiday season | TechBuzz by AT&T can i buy a phone for someone else