Background Rectangle Problem

Hi I used a white background to put my transparent images onto and when i got the proof it looked like Sticker Mule had "removed" the white background so that the images would be printed "direct" onto the t shirt as has happened in previous orders. But when i received the t shirt its clear the white background has been printed onto the shirt with an obvious white rectangle there spoiling the look of the shirt. (The other t shirt in my order Sticker Mule did remove the blackground and was excellent) The printing colours were gorgeous and very high quality and i do try my best to remove the background colour with background remover tools but they left many errors so i always leave it to your skilled staff to remove the background but unfortunately i now realise the staff do not always remove the background colour as standard practice so i will hopefully learn to mention this in the comments when sending a proof. Thanks again for your great company, i really enjoy ordering from you ! Darren