Refusal to honour Entertainer voucher

I purchased the Entertainer app, which gives one 2for1 deals at various restaurants for a calendar year. I saw that I had vouchers for 2for1 meals at Beach Bums and organised my birthday party there promising friends I could get us cheaper meals. However the manager, who had a terrible attitude, refused to honour the vouchers and we ended up paying full price for our meals, and several friends chose not to eat. Completely ruined my birthday and is a complete breach of contract and false advertising.