To receive a call on a cell phone from someone in jail requires arranging for a special phone service that handles the charges, since inmates can only make prepaid calls contracted with a specific carrier, or collect calls, which cell phones don't accept. The first step is opening an account with one of the special carriers. There are various carriers that service jails in different parts of the country.
Once the account is set up, money can be added without a service charge by mailing a check or money order to the service provider or for a fee by paying with a credit card online or over the phone, through Western Union and at some major department stores. Setting up the account will not affect the current phone or phone service, but the service may provide a new phone number for the inmate to use to place the call to the existing phone. Once the account is set up, each call from an inmate is debited from the prepaid account. Some jails also allow inmates to purchase debit cards from the commissary to pay for phone calls; money can be added to these accounts by someone outside of the jail by paying the service provider.