Invalid number when dialing

i am having trouble getting a hold of someone in japan. i dail 011-81-80-XXXX-XXXX because its a cell phone and i connect to japan. after i hear how many minutes i have on my card a voice in english says ''Invalid Number''. This makes me very upset when i think i dial everything correctly. what am i doing wrong or what can i do?

The country code and area code appear to be correct so I can only guess that you actually have the wrong number, sorry- better double check. If it was an actual cellphone number you would not hear that message.

Confusedman,

You don't say where you are dialling from, but I assume you have checked that 011 is the correct code for dialling international numbers from your country.
While obviously it would be worth double-checking the mobile phone number, as Sira says, if you are getting a message in English, then I think that means there is something wrong at your end. If you were dialling a non-existent mobile number, you would surely get a message in Japanese.
If you are using some kind of special phonecard, does it perhaps require that you dial extra codes to use it? That's all I can think of.

I was looking up help all day. I dial 011-81-80-xxxx-xxxx with my card. i would hear a message saying how many minutes i had, that means i connected to japan. then i would hear Invalid Number message 3 right after i connected. everything is correct. its not a problem on my end anymore.
after all day of calling different numbers besides the correct one.. i got it to work!! i was dialing everything correct but it did not connect until about 3:00pm tokyo time. I am wondering is there a time window that i can call? it might be for the cell phone or tokyo's recieving hours. i really dont know.. all i know is to call a little after 3pm. i was going to try and call again at 9pm tokyo to see when the hours end. hopefully this help other people. but does anyone know about a time frame to call tokyo?
also why is the reception so bad? we cant hear anything clear at all. everything sounds like its muffled.

There shouldn't be any kind of time window. Connections from overseas with cellphones are sometimes not so clear. Otherwise I have no idea why you were having trouble calling- it isn't a common problem if you have the number correct, as far as I know.