What is your SIM unlock code? Did it ask you for a 'PUK' code after your third attempts? If it was the case, I am afraid that your SIM has been permanently (and physically) disabled as it usually happens after 10 attempts: you will need to contact your Mobile service provider and ask them for instructions (which would be to purchase a replacement SIM).
Answers & Comments
What is your SIM unlock code? Did it ask you for a 'PUK' code after your third attempts? If it was the case, I am afraid that your SIM has been permanently (and physically) disabled as it usually happens after 10 attempts: you will need to contact your Mobile service provider and ask them for instructions (which would be to purchase a replacement SIM).
Hope it helps: let me know how you go!