Unlock code for Huawei Modem

Hi guys not sure where to post this but am wondering if anyone has had experience with the following. I have a Huawei B528 -23a modem with vodafone thats well out of contract and I'm leaving them as I got a better deal elsewhere that's a sim only package so obviously I want to unlock the modem and use the new sim in it. I was on chat with Vodafone looking for the unlock code and they told me they dont do it and they have no functionality for how to get it. I don't believe this as I've gotten unlock codes for modems before albeit from different providers. I don't want to have to go online and pay for an unlock code if I can help it as I feel Vodafone should be able to supply it for free as I way out of contract. Any thoughts or experience with this?