Euros are used for all transactions in Melilla. You’ll find several banks (with ATMs) around Ave de Juan Carlos I Rey. Most will buy or sell dirham at an inferior rate to the Moroccan dealers hanging around the ferry port or the border.
On the Moroccan side of the border you can change cash at the Crédit du Maroc. There’s also a Banque Populaire with an ATM 200m further into Morocco; walk straight ahead to the crossroads and it’s on your left on the road to the port.
To phone Melilla from outside Spain, dial 0034 and drop the first zero.
Melilla is one hour ahead of Morocco, and two hours ahead during daylight saving time. Most shops and businesses are closed on Sunday.