I bought a SIM card online and went through the validation steps but my I get the message below.
Oops—this isn’t a valid IMEI (phone serial number). Please try again.
The IMEI number should be 15 digits long. You can find it on the phone box, or on the phone underneath the battery.
I checked all possible errors and did not put any letters in the number.
My phone is a Samsung SIII, model GT-I9300 bought in France and unlocked. It works well with my current prepaid AT&T prepaid. Thanks.