Dead Phone replacement

i bought a axesstel sp100 on the 5th of May at cedar square neotel, 3 month later the phone wakes up with a dead screen, i went back to the store for replacement to my surprise the store manager (Khali) told me that they cant take back the phone because the seal is broken. Now if the seal is broken its either i got the phone like that or they broke the seal when they took the phone inside to assess it because i have never opened the phone. i'm stuck with a dead phone, worst part i'm being accused of tampering with the phone.