Rejected insurance

Hi i have a struggle with vodacom. I upgraded my contract with insurance. I have been with vodacom for many years without claims. Now that i lost my phone they do not want to pay out my insurance or give me a new phone. I use my phone for work and have a big contract with Vodacom. All i ask is for them to do the right thing and give me a new phone. I have my contract that shows the money being deducted for insurance every month and i have never not paid them. The reason why they say they will not pay is because the contract is on my mothers name. We set up everything agreed on payment and contract and insurance, my mom afterwards just went in to sign the paperwork. She signed in the box that states that we do not want insurance wich was a mistake, but im sure she didnt know she just signed where they showed her to sign. Still after that i have been paying the insurance as it goes off by debit order. Now when we tried to claim it became a problem. I was not aware of the wrong signatue, or else i would have corrected it from the start. Please tell me what to do in this matter. I need this phone for bussiness.