Access a node from different subnet

I've made a web-application which I installed on a dedicated server connected to our company's LAN. I just have one problem. All the nodes on LAN have 192.168.138.x subnet mask. But wi-fi access point has a subnet 192.168.10.x. If I understand correctly is is because the wi-fi router has DHCP server enabled for security reasons. I tried talking to our IT services provider, but they look at me like I speak chinese to them. What is the best cause of action if I wanted my server to be accessable from wi-fi?

UPDATE:

Router: Juniper ACX1100 Router

It looks to me like you are not in a position to fix this even if you knew exactly how to do it.

Many IT's put Wireless users on a separate subnet / vlan for security reasons. If this is the case and your current IT services provider set it up that way they should know exactly how to make it work through routing / firewall rules, the actual solution is really dependent on how its all configured and the equipment used. If they don't know how then you need a new IT Service provider.

It is also possible your wireless users are on a separate subnet because your current IT Service provider didn't know what they were doing and just installed a WiFi router inside your internal LAN so the wireless clients are doing double NAT (I have seen this many times), in this case you need a new IT Service provider.