How can I check if my phone is unlocked?

[dontwalkhand]

It won't work with Sprint or Verizon SIM cards as those are CDMA networks. However you can take T-Mobile and att SIM cards and shove them in Sprint/VZW phones.
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This makes sense. The phone is locked, but T-Mobile will unlock it for the OP. This just have a 40 day 'requirement'.

Unlock eligibility for monthly phones, tablets, and mobile Internet devices

• The device must have been active on the T-Mobile network for at least 40 days on the requesting line.

Would they still unlock if I owe money on a payment plan?

 

[Applejuiced]

[QUOTE="dontwalkhand, post: 24048171, member:
[doublepost=1481397681][/doublepost]
Would they still unlock if I owe money on a payment plan?[/QUOTE]

I doubt it.
T-Mobile denied me cause my iPhone 7 is on EIP payment plan.