Ubuntu internet connection

[carolkotze0 at gmail.com]

Good day

I sincerely hope you will be able to help me as no one else can.

I live in South Africa.
I had only Vista Basics on my eMachine E510.
Connected to the internet with a Samsung J700 on MTN Prepaid (SA).
Installed Ubuntu.
Should have compartmentalised.
Deleted Vista Basics.
Now I can't connect to the internet with the Samsung.
As soon as I plug in the cell a warning appears that I'm disconnected.
The Mobile Broadband on the list shows that it is disconnected and  the MTN connection is available but there is no signal next to it and it still says GSM Network is disconnected.

My friend's Nokia connects immediately.
Is there something I can do to let the Samsung work?

PLEASE HELP!!

Thank you so much.

Regards

Capol K