Theft on my card from Avis Malta

On the 04 July 2017 i paid the FULL amount upfront to rent a car during a holiday stay in Malta. i have a receipt from Avis to prove this as well as proof on my bank statement. We used the car from the 10 August to the 22 August. Then two weeks AFTER my return from Malta my card was debited with the FULL amount for the second time! When i went through the official channels, customer care, they contacted the Malta office and Malta came back to say the charges are for the rental and baby seats. However, i have proof that i have already paid these costs upfront and in full! It has been weeks and there is no assistance or resolution. They have committed theft on my account and are not assisting in a refund. There is no one official helping me and no end in sight. This company is dishonorable and dishonest, they have ****** this money from my account without my consent after having paid in full upfront.