Recently bought an iPhone 6s Plus refurbished to replace my iPhone 7 as I broke it. The 6s plus has quick battery drain so the shop replaced it with another unit and that was doing the same than I awapped to a 6s and the same issue Tga another but again still the same issue. The reason why went back a model as they were half the price as a brand new 7. Does anybody know if you can go back in model number or is it another issue? Thanks in advance.