How to evacuate the tenant and claim your pending rent amount

We own an office and it’s rented out to a company. The tenancy contract has finished on 4 April 2018 and the tenant is not answering his emails and calls to hand over the keys.

I don’t know if they are in the office or no. This tenant has not paid rent for more than six months now. Only one of his staff was in touch with us since last six months and he has disappeared.

The staff has been giving us false promises and we have been trying to work with her, but this has taken too long and we have lost our patience. The staff claims they cannot pay the rent because some of their clients are not paying them.

While I try to be understanding, the tenant refuses to pay even a portion of the rent or even the AC utility bills, which according to the rental agreement are the tenant’s responsibility.

Can I get to the office as the tenancy is expired now and we haven’t received the rent and communication from the tenant?