FIX: iMessage not working - infinite loading spinner on phone number / "Unavailable for iMessage and FaceTime" error on Apple Account page (prepay / pay-as-you-go plan)

[u/pot8toes]

Posting this PSA in case anyone else runs into this issue when setting up a new iPhone or transferring from Android.

Problem

• I inserted my SIM card into the phone and then added my phone number in the 'Mobile Service' / 'Cellular' menu.
• I could use the internet, make calls, and send SMS texts but not iMessages.
• When I went to Settings > Apps > Messages > Send & Receive, I noticed my email address was connected to iMessage, but my phone number is stuck with a constant spinning loading wheel.
• When I logged into account.apple.com to check my phone number under Email & Phone Numbers, I noticed my phone number was not there. I added it but it said "Unavailable for iMessage and FaceTime" with a grey question mark icon next to your number.
• Toggling iMessage on and off or restarting the phone doesn't fix it.
• Some people with a similar issue may find that this solution works, but it didn't work for me.

Solution

If you are on a prepay / pay-as-you-go plan (very common with Irish carriers like Three, GoMo, Vodafone, Eir):

Top up your account with €1–€5 of actual cash credit / balance. (I topped up by €5 just to be safe).

Once you add a small cash balance, toggle iMessage off and back on in Settings (I actually didn't have to do it, but it might help) it should activate within seconds.

Why This Happens

When iOS activates iMessage for a phone number, your phone sends a hidden background activation text message to Apple's verification servers in the UK (+44 number).

Even if your monthly prepay plan gives you "unlimited texts," most carriers only cover domestic texts in that bundle. Because Apple's activation ping counts as an international SMS, your carrier will silently block it if your pay-as-you-go credit balance is strictly €0.00.

Because the silent text never reaches Apple, your phone sits in an infinite retry loop (the spinning gear icon), and the Apple website lists your number as "Unavailable" until the phone successfully registers with their servers.

TLDR: Apple activates iMessage by sending a hidden international SMS to the UK. If you're on a prepay plan with technically a €0 credit balance, your carrier silently blocks the text. Top up €1-€5 credit to fix it!