Dishonest MTN

MTN Phone me telling me it time to upgrade my phone, i went ahead and upgraded. this month i saw that Almost R5000 rand was deducted from my account, on querying it i saw that last month was the same i just never picked it up. No wonder i was short. On querying this, they informed me that both my devices are being deducted as i upgraded earlier. I was not notified that both devices will be deducted. they seem uninterested to assist me in this , i do not see how this can be legal i did not agree to pay both my devices if this was the fact i would not have upgraded.