What is THIS packet switched data calls

<p>All of a sudden I get billed for packet switched data calls on my COMPANY PHONE... I hop MTN knows that this may cause my job as I have no idea what the hell this is for??? I DO NOT (again) DO NOT MAKE ANY VOIP, WHATSUP OR SKYPE CALLS on my device. From 7h30-16h30 during the day I am on a Wi-fi network. Where and for what is this? I asked via mails and facebook page and called the call centre but I get NO feedback...</p> <p> </p> <p>Do you have a thing like customer service?</p>