Iranian SIM is cheap and you might find yourself in sudden need of Google Maps, so I highly recommend it. You can ask at your hotel/hostel where is the nearest Irantel. The basic SIM costs 10 Euros and includes 2 GB of internet.
You might also download the Telegram app if you want to make staying in touch with your new Iranian friends as smooth as possible. Iranian use this app to communicate, instead of texting, as it’s encrypted.