MTN ARE ****

So i have been using mtn for over 20 years now. On February i decided to by a Galaxy A36 on contract which cost alot. On sunday 26 april i lost it due to someone how break in my car with out using force and took it. Now mtn with santam are refusing to repay me they say it was my nigligent to leave it on my car and i dnt hv proof of force break it..