connection issues

Hi,i stay in the southern suburbs and i have used cell c prepaid internet with a modem before. For the last month if not more im starting to have very bad connection issues. It takes me 5minutes,sometimes more just to log on to a webpage. This is really frustrating as i am a final year student and i need to finish my assignments, which i can't do because of the connection. Could you please tell me what the issue is. Thanks