Did the firmware definitely install completely, or could there have been some kind of glitch? Sometimes an update installs but doesn't fully apply to the system. Try restarting your phone by powering it all the way off (not just turning the screen off, actually shut it down for about 30 seconds), then turn it back on. After that, check how the magnets are catching.
If the restart didn't help, you should check the magnetic module on the iPhone itself. Sometimes dust or debris builds up between the magnets, which prevents proper contact. Wipe it gently, without anything abrasive - that might help. Also make sure the accessories are either original or at least certified - cheap knockoffs often don't work right.
If none of that works, then yeah, repair might be needed. But first try the restart and cleaning - those are the basic steps. If the phone is less than a month old, the warranty should cover it without any questions.