Mastercard extends all chargeback rights to all card types. In the case of services not rendered the 120 day clock starts ticking from the later of the transaction date or the promised completion date of the services not to exceed 540 days from the transaction date. This extra time allows for a customer that may prepay for materials (e.g for a home improvement project) with an expected completion date in the future that extends beyond 120 days.
Bottom line, as a Mastercard issuer you have a contractual obligation to assist your cardholder. Since Reg E doesn't apply, you can require that the cardholder jump through all of Mastercard's hoops including contacting the merchant and writing a detailed dispute letter stating what was supposed to be provided and when, what was actually provided, and the results of the attempt to contact the merchant including the merchant's response.
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