Vodacom failed to meet my needs

I bought a WiFi router at Vodacom south gate in may, it's June now and suddenly it's not charging. I use this router for work purposes. When i bring it back to be replaced or for them to refund my money, they telling me i signed warranty forms which i do not remember signing or being explained it to. A technician sold me this device instead of the sales consultant.

The manager here or supervisor by the name of Venese tried to get me to sign warranty form on the sport telling me they do not keep documents in the shop.

I want steps taken due to the fact that vodacom staff can not do their job. I need my device replaced or a refund. Venese does not know her job. And gave me an attitude.