Can I use a regular T-mobile SIM card on a dual sim card phone ?

What is Mobile Phone model?If the Phone is an Locked Phone you cannot use other GSM Network Sim card in that Phone...If the Phone is an unlocked Phone means you can use any GSM Network Sim card in the Phone...To get the Locked phones unlocked from network lock use the unlock code.Get the unlock code from here Mobileunlocksolutions.com and unlock it.