Cell C
Sim Card Suspended - No Airtime

I purchased a 3GB Data Voucher for R399 in September 2012 for my Ipad 2, The invoice states that the Airtime window is 365 days. I was told by the CellC call centre consultant, this morning, that my sim card has been suspended because I do not have any airtime loaded on this sim. I have 1.4 GB of data available.
Why do I need airtime when I only use the sim card for Data, and it states the Airtime windows for using the data is 365 days? This was never explained to me when I bought the voucher.

Company: Cell C
Country: South Africa
City: Johannesburg

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