MicroSIP - open source portable SIP softphone based on PJSIP stack for Windows OS.
MicroSIP is allowing to do high quality VoIP calls (person-to-person or on regular telephones) via open SIP protocol. From cloud of SIP providers you can choose best for you, register account and use it with MicroSIP. You'll get free person-to-person calls and cheap international calls.
Main in MicroSIP:
If you want the number for that sim card to ring to your SIP phone,, I think what you are looking for what would be called a SIP GSM gateway or ATA . A quick Google search came up with this that does 32 SIM cards https://www.amazon.com/dp/B00P90R5C2/ref=cm_sw_r_cp_apa_i_9RxsFbVHBG7P5 .I think it would be easier if you used the sim card for a data connection and have your SIP phone register to a proxy, but that would be a different number than what the sim card is for.