Dual SIM

I would appreciate if someone could let me know whether dual SIM option for iPhone 11 Pro can be enabled even if a provider in Serbia originally sells a device without this option?

I was happy to see that all network providers got new iPhone models and was happy to upgrade old one and stop carrying two devices with me all the time but for some reason all sellers claim that there is no dual SIM option. I called several times to double check but everyone claims that in Serbia you can only buy without that option which confuses me. Can anyone please explain whether I can buy iPhone 11 Pro and then have it upgraded to become dual SIM??? 😳