The insurance company is obliged to pay your medical treatment costs including VAT. If they refuse to do so, you should claim the refund.
It appears to be that some insurance companies refuse to pay both the medical treatment costs and the respective VAT. Specifically, they appeal to the conditions of the insurance contract under which taxes, fees, stamp duties and other related costs, which arise during the operation of the insurance contract, should be borne by the insured person and not the company.
However, the General Secretariat for Consumer Affairs has confirmed that VAT is not included in the conclusion of the contract and is an independent tax service which is not part of the insurance. Thus, it is not included in the insurance contract but should be paid fully by the company. An exemption is being made if it is referred clearly and explicitly in the conditions of contract that VAT will not be paid when claiming compensation.
For this reason, the General Secretariat for Consumer Affairs has imposed fines on law-breaking companies.