bad service and not considerate

I think it is unfair what Mango did to us in December, we booked flights To Cape town and 2 days before travelling we received sms confirming that our flights were cancelled and we tried following up and found out that flights were on certain days and at that stage we could not cancel or reschedule Accomodation but instead booked another airline. I personally fell that because Mango inconvenienced us ,the voucher was supposed to be valid for a year not 6 months cause at this stage we not planning to travel and with Covid its worse the money was already used to book another airline and due to that I would like Mango to look into that.