The pilot wrote an article in the safety magazine for his colleagues how he misheard the heading for flight level clearance. Instead of turning to heading 080 ("Turn right heading zero eight zero"), he CLIMBED his aircraft to flight level 080 (as if he had understood "climb flight level zero eight zero"). Thus his aircraft came into conflict with an aircraft that was descending to FL070 and this had to be solved by ATC. In hindsight, the pilot agreed that he mistakenly took the heading for a flight level and wrote extensively about this in the safety magazine of his airline company.