Since your phone is listed as being available only in Germany, Australia, and New Zealand, I'm going to assume you're not in the US. So what I'm going to say here may not apply, since I'm only familiar with how things are done in the US. And apologies ahead of time if this is overly basic, but it can be hard to judge without too many details.
Is the phone on a major wireless carrier, or is it a no contract provider? If it's on a major carrier, you typically don't just buy the phone from someone else, because then your calls get billed to your friend--unless your friend cancels the service so as not to get billed, in which case you have a phone that doesn't make calls. If it's a no contract service, you need to make sure you have minutes in the bank, since you typically pay for airtime ahead of time.
Does the phone have a SIM card? For GSM phones, you need a SIM card in order to get service. The SIM slot is under the battery. Here's a link to the manual--see page 25:
LG Optimus Black Manual / User Guide
Are you sure the phone had service when you bought it?