CheckIMEI-Arg Message
IMEI management operations. This service is used between the VLR and the MSC, between the MSC and the EIR, between the SGSN and EIR,
and between IWF and EIR to request check of IMEI. If the IMEI is not available in the MSC or in the SGSN, it is requested from the MS and transferred
to the EIR in the service request. This service may also be used to request the BMUEF from the EIR. The service is a confirmed service and consists of four service primitives.
Reference: TS 29.002-f30