Poor customer service

I recieved email of tax from Buffalo on the 11th of March, which I paid the same day. There was no update of tax paid on order tracking. I've called, whatsapp them many times. Sent them proof of payment through email 5 times, and I upload POP on my order 4 times (different date). Still no update of tax paid and I'm still recieving email that says I need to pay tax which I already paid 10 days ago. The worst part is that, they are not responding my email😩.