@divramod 

Hi, thank you very much for the feedback.

Could you please confirm if there is still Vodafone 3G signal in your area? You could try to change Network Type on MR600 to be 3G only to see if there is still any 3G signal received and if internet still works.

Please note that the USSD is based on GSM network, which only works under 3G/2G network, while the MR600 doesn't support 2G, so the USSD only works with 3G on MR600.

By the way, when you uses USSD on your phone with the same SIM card, please also check if the network falls back to 3G or 2G on the phone.