Depends on your Nigerian network if it allows you to call out, but bare in mind that it cost way to expensive so better use a local landlines or phone cards.
Hope this helps.
To call a mobile phone that is roaming in the United States, you dial the number the same way that you would if the mobile is in its home country. The same is true no matter what country you're roaming in.
When a mobile phone is roaming in another country, you dial its number exactly the same way you do when it is in its home country. The mobile network will automatically find the user, and the roaming user will pay any applicable international roaming charges.
Dial the number exactly the same way you would if the other person was in Australia. The mobile network will locate them wherever in the world they are roaming. The easiest way is to program the number into your mobile in full international format (in this case, replace the trunk prefix 0 of the Australian number with country code +61, including the plus sign). That way, it will work even if you are roaming in Greece or Japan or Argentina.The same principle applies for any mobile phone from any country, roaming in any other country.
If a Nigerian mobile phone is roaming in the United States (or anywhere else in the world), you can call it by dialing the Nigerian mobile number, beginning with country code +234. Drop the trunk prefix '0' from the beginning of the Nigerian domestic number and replace it with country code +234. If a mobile from anywhere in the world besides Nigeria is roaming in the United States, you cannot reach it by dialing a Nigerian number.
If the Dubai mobile has international roaming, it can be called by dialing the UAE number, country code +971. If you want to reach that phone by dialing a UK number, you may be able to swap in a UK SIM card.
Customer care to enquire about roaming
If you are moving, you will most likely want to get a UK mobile number. However, if you are only going for a visit and using the international roaming ability of your mobile, then anyone who wishes to call you should dial the same number they normally would when you are at home. The network will automatically find you wherever you are roaming.
Just dial the US cell number, whether the US cell phone is at home or halfway around the world. The cellular network will automatically find the user, if he or she is in a country with a roaming agreement, and the roaming user will pay any applicable fees.
A mobile number that goes directly to voice mail could easily be disconnected. In the case of nonpayment, an interrupt message is received. When a number of rings are heard before the voice mail message, then the number is working.
London (UK). Highest number of sales there and more than 700 cars roaming around in london. The highest compared to any state in any country.
You dial the U.S. cellphone number exactly the same way you do when it is in the U.S., no matter where in the world it is roaming. The cellular network will automatically find them, and the roaming user will pay any roaming charges, according to their calling plan. The downside is that someone in the UK also has to dial the US number, even when the US cellphone is in the UK.
If everything works as it is technically and legally supposed to work, the number should be withheld. However, technical glitches are always possible.