I visited Zagreb, Croatia fall 2019 and needed a SIM card for my cellphone. I was there for 9 days. Hrvatski Telecom (T-Mobile) had on their website 7 days of unlimited internet for 85 kuna (11 €). I agreed to that and also paid 15 kuna for minutes of talking. I also said that I needed more time and asked if I could pay now for the extra days.
The gentleman said to wait after 7 days and then recharge for the extra day which was 10 kunas. It even says that on their website. The seven days were up and I returned to the same store. This time it was a female and told her what I wanted. An extra day for 10 kunas. She told me this offer does not exist. She said she can add three days for 30 kunas. I reluctantly agreed and paid the 30 kunas believing that I will get three more days.
Well, one day passed and my internet was gone. I don't remember if I could make a phone call either. Conclusion, she knowingly lied to me and charged me three times the amount for the extra day I wanted. Probably took advantage of me because my Croatian was poor and also I was a tourist. Stay away from that store and even T-Mobile S!mpa. Try A1.