[Why Aitch]

Hi. I've Googled and with Verison there is an option under call settings to turn video call on or off. There is no option on my Galaxy Note 4 (Optus Australia). Phoning Optus the technician said it can't be done as it's a factory set feature of this model. I don't like it because:
1) I NEVER use video call
2) 5 times this year the feature has engaged automatically at the end of a standard mobile call ringing the number I've just ended. Each time I get charged $1.40 by Optus.
I wish I could add screenshots to this post to assist replies/assistance, but I can't.
Thanks in advance everyone.