Cancellation query

In June 2017, I took out a smartbroadband month to month (sim card only) deal with Telkom at their Greenstone branch... I was told that I could both upgrade & cancel it at any point. However, now that I requested a cancellation, now all of u sudden I get the following rely "Thank you for submitting your details, please be advised that line 081******* still has 5 months and 9 days, Meaning you will be liable for cancellation fee, your case number is 215***** and feedback will be communicated“..... ABSOLUTELY NOWHERE on my copies of the forms does it say anything about it being a 12 month contact & I refuse to pay anything extra. I will be putting a stop order through. I'm not paying for something I canceled