Sudden SIM error when using a modem

Hi Gurus,
My modem was working perfectly fine when just a while ago I got this error message. I haven’t changed nor touched the SIM inside it and so I wondered why I got this error.
Need your help as I couldn’t connect to the internet and still have to go to an internet café. I wouldn’t want to buy a new one since this modem in error is fairly new.
Please help resolve.

Prompt
Only the specified SIM/USIM card be used on the device!
