Missed payment - rudeness an no explanations

So where do i start? On the 28.7.19 I used my card for the first time. In mid August I received a sms with my account details with the payment due on 30.8.19 about 2 days later a received a sms with my balance due with almost dubble the payment amount, I made a payment 1.9.19 and later I received a sms saying my account is now overdue?!?!?! Please explain to me, how is it possible if I used my card for the first time end of July I need to make a payment on or before the 10 of August?! Is this even possible? Rather I'm being called by rude unprofessional people claiming I missed a payment! I've stoped arguing with them And agreed to pay the "missed payment" So now I've made the necessary arrangement to pay the account up-to-date and they still call me to ask when am I going to pay the "outstanding" payment? Aren't they communicating with one another or what is going on???