Connecting two offices having two different Internet connection but common IP PABX

[AbdulMannanKhan87333]

Recently I installed Cisco SG350-K9 Series Managed Switches 52 port in both offices.

Office A (Old office)

Equipment's:

1 Cisco SG350- 52 port Switch (192.168.1.1)

2 FTTH 200mbps Internet

3 Dlink IP Telephone PBX

4 Telephone 1 line. to use with office A only

Office B (New office next building)

Equipment's:

1 Cisco SG350- 52 port Switch (192.168.100.1)

2 FTTH 200mbps Internet

3 Telephone 1 line. to use with office B only

I want to connect both office with SFP Port only to share the same IP PBX.

Please suggest me how can I do it to avoid any conflict between two switch and solutions 

[balaji.bandi]

You can extend the link using uplink SFP with the right optic to support your distance to connect both the office.

make the port as a trunk.

how is your setup both the office is there any Specific VLAN configured ? or both are VLAN 1? - in this case, we need to configure point to point interface and use the static route.

post both the switch config if possible.

[AbdulMannanKhan87333]

Thanks BB for your reply,
Yet I didn't configure the switch it is still as default config only IP address are as mentioned above.

Switch A is 192.168.1.1 (Default Gateway from Internet router)

Switch B is 192.168.100.1  (Default Gateway from Internet router)

The only purpose of network is to use internet & IP telephone for all users