I had an order from Temu,then on the 3rd of June I received a message from Linex Air Services to pay customs of R463

I had an order from Temu,then on the 3rd of June I received a message from Linex Air Services to pay customs of R463.35 then I chose payflex method of paying in four installments and I paid 2 installments that day and the next installment was on the 17th of June they tried to deduct the amount from my bank account and it was not successful and that same day around 2 pm i made a payment and i received an email from payflex saying the payment was successful and later that day i paid what was supposed to be my last payment and it was also successful...the problem now starts when Linex is saying i did not pay my installment on time and that i was in arrears, how can that be when i paid on the agreed date i dis not pay a day later...now they keep sending me massages saying I owe the close to R300 for a late payment, and now they are trying to double that R463.35...and i have been trying to contact them so that wen can solve this and i did not get any help and i have proof that i paid ont the agreed date.