WIFI Router contract

I have a cellphone contract which I had an early upgrade in August of which my contract is due in November. A week after I received my cellphone they then offered me a WIFI router which I was happy with but because on my cellphone contract I upgraded the data I was receiving. Now when they were offering the router I then asked them to downgrade the cellphone data and after that I can upgrade the data on the router. I was told that I cannot change the data before the actual date for the upgrade. Then I asked them to upgrade the data on the router. It has been up and down, I then went to the store and they told me I cannot upgrade the router, yet the lady that sold the router told me I can change it any time. At the store they said I was given false information. they said if I want to change I must pay about R900 plus. They gave the contact no for the manager of the lady who sold the router to me and when I called the guy was mean and rude, I doubt he's the manager, he later then said he cannot help without me giving him the name of the person who gave me his contact no, which I don't know what does that has to do with helping me.