Client Refused To Make Payment Of Given Website Services...what Next?

Hello Sir/Ma'm, I am a web designer. I am serving my client (reputed hotel in Vadodara, Gujarat) since 4 years, i am renewing domain (website name) and hosting services on behalf of them on postpaid basis due to good relations. But this time client fails to make payment even after 5 months of invoice date, i have reminded them by calls and emails but they refused to give payment, i have renewed services with my money, i lost that money. What should i do? I have temporarily suspended hostinf account of that website due to non payment, but can i sell their domain name to other? I haven't signed any contract with them, but i have stated "Terms and Conditions" into my website that if client fails to make payment after 1 month of due date then domain will be fully owned by ours. Will it be legally helpful to me? What should i do?