All the work visit visa is valid for 6 months to enter the country. If u r not interested to join the company let them cancel ur existing work visit visa. Else u can wait to get the automatic expiry of the visa, if u hold a valid visa fm one company, obviously u will not get the visa fm another company. In case if ur present company (who holds ur visa)is not cancelling u can contact the Labour & Immigration department to help u out. Better option requesting the company who holds the visa, because there is posibility to renew ur visa validity period