Poor Service

I booked 1 tickets online last night 2022/02/08. I realized I made a error with the dates. The outbound flight was booked for 02 April instead of 01 April. Went online to get contact details of Travelstart, no contact number. Submitted the online form, stating what I would like to do, Did the same on the whatsapp line still no assistance from them. Contacted the Airways Company but they cannot help as the flights were booked by a travel agency. So basically Travelstart offers no after service. This was the second time I have used Travelstart. The first time was a dream now it is a nightmare.