DATA/2 X HEADSETS BEING CHARGED

I recently upgraded my phone from an iPhone 4 to an iPhone 6 - this was done in January although my 24 month contract only expires in March. Upon receiving my statement for January, I noticed that I am being charged for 2 x headsets (and this is 2 different amounts). Every other time I have upgraded, the one headset falls away and you only pay for the new one - so why am I now paying for 2? And if it is the case of the initial iPhone not being fully paid off yet, why are customers not informed of this before they choose to do their upgrades? If this is the case I would've left my upgrade until March!!!!<br> <br> Regarding data costs, on my last few invoices I noticed that my data charges have been EXTREMELY high - even although I purchase a monthly data bundle for my number. On a few occasions I get SMS's from Vodacom telling me my data has run out and I will be charged out-of-bundle rates, however when I check my balances, I still have more than enough data left?!? What is the situation here??