DISMISSAL: Insubordination - Claimant refusing to do a relief period - Reasons for the same - Effect of - Whether his refusal had shown insubordinate conduct on his part - Whether it had been established by the company - Effect of - Evidence adduced by the company - Whether sufficient to satisfy its burden of proof - Effect of - Whether dismissal without just cause or excuse - Industrial Relations Act 1967, s. 20(3)