Strata Managers Authorised work without approval of OC

A tenant in a rental property reported some water ingress to their rental agency. The rental agency submitted a quote to the Strata Managers for the work to be done. The strata managers sent an email to the OC  with the quote. One day later the OC asked the Strata Managers  for more information as there had been several instances of water ingress in different apartments. In the meantime unbeknown to the OC, the Strata Managers approved the work to be done. The work failed and the builder is now asking for payment as he maintains he was given a scope of work by the Strata Manager.  Who is responsible for payment, the OC or the Strata Manager.