Kazam, for those that didn't know, is a UK-based phone manufacturer founded in 2013. Their goal is to provide a smarter, sleeker, and streamlined brand of devices, and to innovate in areas where "others" have overlooked. Unfortunately, Kazam is overlooking Windows 10 Mobile for their existing line of Windows Phone devices.
Kazam currently has the Thunder 340W, Thunder 450, and Thunder 450WL -- but will not be offering an upgrade to Windows 10 Mobile for these devices. According to a report by WMPU, a spokesperson for Kazam simply stated, "we won’t upgrade existing product to WP10 but all of our new WP devices will have it going forward." No reason was given as to why, but Kazam did mention that they have a strong relationship with Microsoft.
Kazam has previously confirmed that they would be launching new devices powered by Windows 10 Mobile. BLU, another phone manufacturer, will provide an upgrade to Windows 10 Mobile for two of their most recent Windows Phone devices -- Win HD LTE and Win JR LTE.