Bad customer service

Good day, I went to the bed shop(Ormonde/Xavier) to purchase a head board on the 13th of August I left them with a R100 for laybye. So I went on Monday the 17th to tell them that I can't afford the headboard anymore, instead can I buy a pillow with that 100. But the store manager refused me saying they have already set aside the headboard and it needs to be bought, I gave them my reason of why I can afford it anymore but they just don't want to understand, also they first gave me an excuse that my 3 months of laybye it's over while it wasn't was still on 2nd month. Please guys I need your help... I know 100 is a small money but it makes a difference in my life, you help will be highly appreciated. If I had said I wanted back that 100 I think they had every right to refuse me but no I'm asking to buy something else. So they rather force me to buy something I no longer afford. HELP... The supervisor number is ***