For my understanding, your unit is Pepwave Surf SOHO, right?
In this situation, you have to ask ISP to add the static route for you 2nd subnet. For example, WAN Interface IP of Pepwave Surf SOHO is x.x.x.121. Your ISP should need to have add the following static routes.
x.x.x.221/32 via x.x.x.121
x.x.x.222/32 via x.x.x.121
x.x.x.223/32 via x.x.x.121
x.x.x.224/32 via x.x.x.121
x.x.x.225/32 via x.x.x.121
x.x.x.226/32 via x.x.x.121
- Because your IP range is x.x.x.221-226 and it is not in same 29-bit network, therefore your ISP have to add them one by one.