Some people will never be appeased. They will complain about everything. It doesn’t matter how much you go out of your way. You can explain to them why something can’t be done, but then try to make it up to them in another way that really over-compensates for everything. Still, they bitch. You also do them a favor by facilitating a deal that doesn’t even involve you. No need for thanks. Instead please just don’t harp on the shipping, which is much better than the other guys’. Seriously, consider the alternative. Consider what went into accommodating you. Again, no need for thanks. Just don’t complain.