help

I have to prob with travelstart! they r to lasyyy and that is not good! I've beyed a ticket from momondo but I haven't attention that the flight date was not good! I've called so many time and waited 20mn no one responde that was yesterday and today I want to cancelll the reservation how can I doo?? Travelstar really I don't anderstand why u don't respond I've payed with my Mastercard I want to cancel the fly plz call!!! The fly is next week and I want to cancel it