Someone who does not accept order after complete work


hello there i have one problem .

is sending me order for install paid plugin and install paid theme in cheap price

but after i complete work then first of all he give me 75% $ and in that he want to cancel 45$ order then

i haven’t got nothing,and he told me i am cheater and here i give him 350$ price thing in 120$ on that he don’t want to send next 45$ order and want to cancel last 45$ order .

please help me sir