Problems with Vodafone's Prepaid GSM Line Switch

I have a problem with Vodafone that must be resolved. I've been trying for a week to switch from a postpaid line to a prepaid line, and I'm about to give up. I've had numerous conversations with customer service representatives, but they either hang up on me or talk about things that I don't understand. The dealers simply state that contacting customer service will resolve the problem. I'm sick of calling and getting put on hold. I currently have three Vodafone lines, but I'm seriously considering canceling all of them. Is the process as difficult as it appears? It's disheartening that we haven't received any responses to our inquiries.