Telkom the bridge, zero amount invoice

Can someone please help me understand how one can pay R50 for a sim swap and not receive an invoice that states that I've paid???? I visited Telkom at the bridge yesterday, asked for a sim swap they then told me it's R50 that I paid... They initially told me the printer is broken and can't print. They promised to email it but they didn't. I go in today, now they can print. But there is no amount on the slip? That to me is a little suspicious. Please can someone explain