I have bought a pair of heated socks with batteries I have just started using them and am find that the batteries are not preform any where like the advertised duration I have contacted the vendor hand have asked for replacements the answer that they have stated from there technician is the batteries cannot be shipped alone but has offered a 10% refund to obtain replacements I know that if I can find replacements they will cost more than the 10% offered what should I do?