I bought something worth N240, gave him 300, he gave me 50 n said he doesn't have 10, I left, I came back n gave him back d 50 n told him to give me 100 out of d 300 I gave him so DT I can make change, he did so n now he has 250, since wt I bought is 240 he stl has my 10, after making change, I came back n gave him 40 so DT he WL gv me 50, BT after giving him d 50 he said he is not owing me,DT it has balanced, is he not supposed to give me 50