Not charging service tax in bill by service provider

We are a ltd company. our service provider (for repair and renovation of office building) is an individual. He is not charging service tax in bill raised by him though the single bill for entire work itself is in excess of Rs 10 Lac. in such case what is the way out for us. As this is covered under RCM we are paying Service Tax on 50% value;works contract. But can dept hold us liable for not paying service tax .our problem is that until and unless service tax is charged in bill how can we pay;except our liability under RCM. please help...