The Huawei B525 router for the 4g wireless broadband has no apparent DNS settings in the web user interface (UI).
The DNS settings are available, and will work, they are just hidden in the Web UI.
The following steps will enable these and allow you to set them.
Step 1. Go to the DHCP settings screen of the router using Chrome
Step 2. Press F12 to enter developer mode, and enter the following in the Console.
$('#dhcp_dns_statistic').show();
$('#dhcp_primary_dns').show();
$('#dhcp_secondary_dns').show();
Step 3. Press F12 again to close the developer options
Step 5. You can now enter your own DNS settings and click the [Apply] button
That's it!, DNS settings should now be applied and your router should be restarted.