Trying to set up two SIM cards

I have been using an AT&T SIM card and data plan. I want to add another card from Verizon so that I have more reliable coverage. Verizon told me the IMEI isn’t supported, but then said it was locked by AT&T. I have tried without success to get AT&T to unlock it - their latest excuse is that they cannot unlock a device until it’s been in use for 6 months.

Has anybody experienced this before? Do you have any advice for how to move forward with this? Is the “unlock” story for real or am I getting blown off by people who don’t know what they’re talking about?

Has the Pepwave MAX Transit 5G Router been verified by Verizon? In which case that lends more credence to the unlock issue.

For what it’s worth… here is a list of the devices certified for use on the Verizon network.
https://opendevelopment.verizonwireless.com/device-showcase
A locked Peplink device on any cellular provider raises a variety of questions. Did you buy the device from an authorized partner? If so they should be able to provide some assistance.

I’ve using a Verizon & ATT SIM for over 6 months on my Peplink MAX BR1 5g PRO without any problems even before Verizon was certified. The SIM came out of my Novatel MiFi 7700. The Peplink was purchased from Amazon.