Travelstart NOT RESPONDING to urgent need to postpone flight

My sister and family have been planning a visit to our country for ages, not having seen any of us, nor my brother in law's 90+ year old father for 2 corona years. An expensive trip but they want to make sure they seem him as long as he is with us. As luck would have it, in the preflight testing their boy was found positive for covid, and they have to postpone their visit until he is out of quarantine, BUT their flight is tomorrow, and they have been on the phobe with Travelstart since they got the test results, and NOBODY is answering them. Will they end up losing their tickets because their agent, Travelstart, provides NO SERVICE in such a (probably very common) case? If they are unable to reschedule, I doubt they can afford to come at all. Will my brother in law see his dad again?