Sierra HL7588 - IMEI device number not recognized by Verizon

We have integrated the Sierra Wireless HL7588 cellular chip into the design of our new product. The problem is that we tried to purchase a SIM card from Verizon (HL7588 supports Verizon and AT&T) in order to start testing the cellular service on our device. We gave the sales rep at the Verizon store the IMEI device number of the chip and it seems that Verizon does not recognize the IMEI device number for that particular chip. Is there some other device numbers we should be using in order for this chip to be recognized by Verizon or have these IMEI device numbers been updated with new numbers? Any help is appreciated regarding this issue.