Poor service from their agents

I made a booking about a week ago and tried to add an infant to that booking but I cant seem to get help. I received a couple of emails from Kim Dullisear until she decided to start ignoring my emails up to date. She just told me to contact the airlines direct she cant help me even after I sent emails to her from the airlines direct that I should get help from travelstart because I bought my tickets through them. I called travelstart again got a bit of help from Sisanda until she also decided to ghost her me. After thats I have spoken to 2 more agents including Yolanda but still noone can assist with just adding an infant to a booking that already exists. Yolanda tells me unfortunately there is nothing she can do she can escalate and I should wait for someone to call like I have been waiting all week. I am just so disappointed at this kind of service and will definitely be not buying any tickets through them again.