I am paying child support but child doesn't live with mother?

I am paying child support about a month ago the childs mother made him move to her mothers b/c she couldn't handle him. She still collects support and refuses to give her mother any support. Now I have the grand mother asking me for support I feel like giving it to her but I already pay support. I was wondering I anyone could give me some advise.I have no problem paying support but would like my son to recieve it. What can I do and should I give his grandmother money for him or not?