I had the same problem a couple of months ago. I called a plumer, he told me to boil water and pour the boiled water into the sink (to melt the oil in the sink), I did and it worked.
I had the same problem a couple of months ago. I called a plumer, he told me to boil water and pour the boiled water into the sink (to melt the oil in the sink), I did and it worked.