MTN ONLINE HOME ROUTER

Got a home router online and I was asked for a delivery address for my router and I explained I wanted it for home so I gave them both my home and work address so they delivered it. When I got home it didn't work so I phoned and asked what was happening and then they suddenly told me I didn't have coverage so I should take it back to my nearest MTN , I immediately did that the next day , received a statement that I returned it and so they told me they cannot help me with the cancellation and I need to call since it was an online application IMAGINE!!!! Okay I called and cancelled it but they've been billing me since February until now? They say I owe them 5k????? Please don't apply for anything at MTN online because they will turn against you.