My N90 is locked in a certain sim . :( i cant insert other sim cards . help me !

Your phone is probably locked to a certain network (i.e. Vodafone) and can be unlocked (after a certain time) by requesting a NAC (Network Access Code) from your old service provider. If you use a phone that is locked to a certain network provider and your phone is NOT SIM free (meaning you can use any SIM in the phone from any network) then you will need a NAC to unlock it from you old service provider.

https://nac.vodafone.ie/

The above link is provided as an example.

to remove the sim card this requires a very small tool or fine needle or fine piece of rigid wire and insert it into the ejection hole located near the sim card.

Hope this helps

one reason might be is that , your phone might be network locked and hence it is rejecting other SIM, If that is the case try unlocking your phone to use other networks, http://www.theunlockarena.com/ will help you with the process

If the phone displays the message 'Insert sim' in which you have already inserted a sim card, it is because the phone doesnot reads the sim card and it is currently locked to any particular network. Nokia 5130 phones are old DCT phones which can be unlock easily and freely through online. Search online or get the code from the site Unlock-Free.com where they are providing free unlock codes for certain Nokia phones.

Are you sure that you are using sim cards that is allowed by the phone as it may be locked to a certain carrier? For example, maybe it is locked to ATT and therefore you can only use SIM-cards from them. If you are trying to use a Verizon SIM even though it is locked, it will give you the error you are describing.
Good luck! :) And please, if you do find this answer helpful please give it thumbs up.

There can be 2 reasons :
1 The phone is locked to a certain network from your country
2 The sim card is expired or blocked

Call your service provider customer relations and ask for the status of your sim card. If your sim card is OK, then the phone is locked. You can unlock it by going to a GSM service.

Do the SIM card and phone come from the same company, or are you using another providers SIM card on your phone?

Most phones in the US are locked so you can only use the provider that sold it to you. You may be able to request the unlock code if your contract has expired. Ohterwise you're stuck with the same phone company that sold you the phone.

this means the phone is locked to a certain network

Invalid SIM and Unregistered SIM are two different problems. Invalid SIM means the phone is locked to a certain company and you are trying to use a SIM card for another company. Unregistered SIM means the SIM card you are using is not active and you need to contact your service provider to get it activated. In order to unlock the phone so you can use anyone's SIM, you must contact the provider that the phone is locked to.

the phone need to re format the software .. you just need a technician to re programmed the unit.. so that all the original file or data be reseted