I have just received a new SIM card I want to use in an iPhone 4S. The phone reports decent 3G connectivity and can make phone calls, but it does not connect to data services. Data services work when using older SIM cards from the same carrier. Also, the new SIM card works when installed in newer phones (testet on an iPhone SE and an iPhone X).
So, out of six possible phone and SIM combinations, the only one not working is the oldest phone with the newest SIM card. All SIM cards are from the same carrier, and the Mobile Data Network settings are as recommended by the carrier, and identical across the phones, except that the oldest phone is a 3G phone, while the newer models support 4G/LTE.
Can the new SIM card be incompatible with older phones? If not, what can the issue be? The carrier support has been unhelpful so far.
Best Answer
I heard back from the carrier. They informed that the subscription for the new SIM card only accepts 4G connections and not older. So these types of subscriptions will work for iPhone 5 and newer, but not iPhone 4S and older.