Repair under warranty. now big bil dor my account

Long story short... Sent phone in for smashed screen and a few small issues, got a quote, checked my warranty and cover, asked if quoted repairs were under warranty and was told yes. Gave the go ahead. Got the phone back after my courier was 1st rejected due to a R200 courier charge I was never made aware of or invoiced for, asked for an invoice, paid, got my phone with a new issue of a flickering and black screen issue. They agreed to repair under workmanship warranty including the courier fees. They collected it. In the meantime sent my hubbies for a screen replacement too. Now suddenly there is an outstanding invoice Of R1200 for my first repair. Now they won't release my hubbies phone either even though there is no outstanding invoice in his phone. I am beyond disgusted. How can they confirm the repairs will be under warranty and then say they are not, how is it they wouldn't release when there was R200 outstanding but are now claiming they released when there was a R1200 invoice outstanding?! This is unacceptable. I have lodged a complaint with Samsung SA