Poor service, non contactability and nobody care.

I am in Johannesburg and was called by a lady form the Vodashop-Vodacare-Durban re an upgrade done about 2 months prior. She advised that the package that I am on will cease to exist and recommended an upgrade. My explicit request/ instruction was that the upgrade should not cost me more than what I am currently paying. She confirmed it will be less and she will add a device which I can return within the said cooling off period. She gave me the contact number ***. I received the device, which was worthless as it would not meet my needs and also noticed an increase in the amount due. I immediately started calling the given number but it seems to be out of service. I tried Vodacom customer care and have been sent from pillar to post. Nobody seems to be able or want to assist me to get the device returned and the upgrade cancelled. All refers me back to the store but there is no understanding that the number given by everyone is out of service. How do I get this sorted out. I don't want or need the device, want the upgrade cancelled and a refund of the monies already paid. I have tried all possible avenues to get hold of the store, from calling to emails without any success. The delay in returning the device is due to Vodashop Vodacare Durban. Why should I keep paying their poor service?