Rude customer service and shady customer service number.

I have an account with pep. So I explained to them that I won't be able to pay the full installment last month and they explained that I couldn't do that because my account is up to date. Even though I hadn't paid. Sharp. They call me a few days later asking me about a payment arrangement. I tell them that I will be able to pay my full installment next month and the lady sets it up and I go about my day. Mind you when I was on the call I was trying to go on my banking app but I couldn't because my bank sent me a notification that they don't trust PEP's number even though I dropped the call. My bank app wouldn't let me access because they were suspicious of the number. That caused my online payments to glitch and I had an authorisation failure. Now they keep calling me multiple times for this payment arrangement even though I had arranged on the first call from them and they told me it was not set up. I told them I don't feel comfortable with the calls anymore and I will set it up online but they refuse, shout at me and are totally rude towards me. I am even thinking of making a complaint to the national credit regulator (if that's the right union). They keep on calling so they increase the funds on my account. Even their email doesn't work. It's a horrible customer experience.