Airtel — sms sending failure

Dear sir,

My number is [protected].

I recently migrated from postpaid to prepaid.

I am based in nigeria presently and using my phone on international roaming.

However, i am unable to send any sms from the line and getting error message - message sending failed everytime i am trying to send an sms.

I have even done sim replacement on the suggestion of a customer care executive and even then it is no improvement.

I need to send some sms to register my banking app and some other work as well
I have called the customer care several times and the only thing they say is that everything looks ok in system and they will forward the request to the technical team. However no one replies or even care to respond.

Please help.

Regards,
Shanky jalan