Invalid sim when you put sim card they not register just apper invalid

Did you buy the Doro second hand? If you bought it brand new take it back to where you bought it and they should be able to sort it out for you, often free of charge.
If you bought it second hand you'll find most mobile phones are 'Locked' to a specific network so you have to buy one of their sim cards. A sim card from another network will not be recognised by the handset and it will give you the "Invalid" message you're getting.
Try this. Turn off the phone, remove the sim card and turn the handset back on without the sim in it. Don't worry this won't damage the phone. There should be a logo or name on the screen showing who the registered network is. If the network is different to the sim card you have the phone won't make calls or send texts.
There is a reasonably easy, (and often cheap), fix for this. Take the hand set to a good phone repair shop and for a small fee they should be able to 'Unlock' the handset to where it will accept any network's sim cards.

It sounds like the SIM is corrupted. You may have to format it and start over.

I just had the same problem. I used a paperclip to open and remove the sim card tray. I blew on the card and the opening to clear off any dust. After re-inserting the card, the device said "No SIM" for a moment then registered and regained service. I hope it helps!

your sim card may not be registered or it may be invalid! make sure that you put it correctly in the sim jeck!

Your cellular provider has to have the phone you are using on file so that the network will recognize your sim card. If you have AT&T you can log onto your account and change it yourself. You can also call and simply say it won't recognize my sim card, they should be able to indicate the phone you are using and it should then register on the network.

Is this a new phone? If so, make sure you are putting the sim card in the correct way (some phones are tricky). If you are attempting to add a sim card from a different network than what the phone is registered through, it often won't work unless you jailbreak it (a whole different solution). This is not legal, and often won't give you full capability of the phone. Finally, if you think it is a problem with the sim card, it might be rusty or dirty. Try lightly cleaning it with a soft eraser from a pencil. Good luck!

before registering my cell phone i used to use 2 sim cards. After registration it allows only my first registered sim card, not any other, even if it is from the same company. If i put another simcard even if it is from the same compan, it gives the messege ``Illegal use. power off`. It is very hard i can't put 2 sim cards and when i travel to another country i have to use another phone.

CAN ANYONE HELP PLEASE HOW TO SOLVE THE PROBLEM?

try a different sim card if that doesent work then it might be the phone

You have to unlock your blackberry, in order to do so, visit http://blackberrymep.com and get your unlock code with instructions to unlock, it's fast and rapid, you will get your blackberry unlocked in five minutes .

your phone is not able to read the sim card....try the phone with another sim card,if it works then this means your main siim card is faulty...if not you should get your phone checked by a technician...