Sorry to hear you've had this problem when trying to register a mobile account for your dongle. To be honest I wasn't aware that the registration involved codes being sent to mobile numbers I thought it was all done by email.
Let's have a look and see what we can do to help get this cleared up for you - just get back to me via PM please (the purple envelope icon) and we'll take it from there.
If it's an SMS text that you've been sent, you may be able to locate it by logging on to the dongle from a browser following the instructions, hopefully, provided with the device. Usually by entering the devices IP address - numeric characters - xxx.xxx.xxx.xxx (e.g. 192.168.99.99) watch out for spaces after the "dot" as it can be handled as a puncuation full stop.
Been a few years since I've played with such a beast but once I jumped onto my mother in laws Huawei dongle, it was an easy job from there