Travelstart disappoints!!

We made a booing from JHB to Glasgow via London a few months ago, our flight is less than 20 days away and we have to reroute to Amsterdam at a later date due to unforeseen circumstances. I have been trying to get hold of the call centre or anyone for that matter for the last 4 days with no luck. Every time we phoned we were in hold for about 20 minutes before eventually hanging up the phone and trying again. Ive reverted to emails with no luck! This seems to be a general issue as there are many similar complaints on the Facebook page. How are we supposed to make changes if no one is available EVER?? I DO NOT RECOMMEND USING TRAVELSTART