firebase phone Auth problem

[syed saif]

when iam hit request to firebase for phone auth otp will come into my moblie but the error say's 

 Unhandled Exception: [firebase_auth/invalid-verification-id] The verification ID used to create the phone auth credential is invalid.

if iam see my project limits iam under in free plan but i dont know why firebase block my Ip some times its says so many request are there from our side thats why its block try again later.

kindly please help me to find solution

thanks for advance.