mobile device protection associated is denying my claim

i have purchased an insurance that says we will replace or repair your device hassle free. i have sent a letter to them describing how the loss of the phone occurred i told them... "My brother Alberto Saravia, the user of the cell phone, was playing soccer with my dad in Zalud Park in Porterville, California. He put his cell phone in a gym bag along with my dad's eye glasses, tennis balls and other personal things. They were very close to the bag, approximately 50 feet distance. While they were playing, somebody stole his cellular. He was reasonable, careful and diligent taking care of his cell phone. Accordingly, I am requesting a replacement of the cellular device within two weeks(14days) of receiving this letter , since we paid the insurance and I totally disagree with your conclusion of "UNSECURED & NEGLIGENT LOSS." so now they have offered me a refund of the insurance but i said i want a replacement of my cellular device a black berry 9000 from AT&T the price of the phone is worth 439.99 and the insurance will give me 50 bucks back and if i get a replacement phone there is no deductible. I really appreciate the help that you are about to give me thank you very much. when saying my brother Alberto saravia the account is under my sisters name but i do all the work that's why it may seem kinda weird