NO SERVICE FROM LINEX

I am really tired of trying to get LINEX AIR SERVICES to respond to my communications. Every other day they send a WhatsApp message to me asking me to pay Customs Duty. I was not aware of this additional payment, therefore have asked them to return the order to TEMU!! I have sent them a message this morning via e mail and will see if they read it and respond. How do businesses continue to survive if they can't respond or communicate with clients?????