Cable modem -> switch -> router and a SonicWall firewall

I need some assistance with our network at the office. We recently switched from having our data and voice being managed through a T1 and a phone server on site to having a cable modem and a virtual PBX.

Previous set up was T1 Line -> Box from T1 provided -> one line to the phone server and a second line to a SonicWall Firewall which then went to a couple of dell switches.

We have switched to a cable modem with 5 static IP's and a virtual PBX. Tech support for the PBX company suggested we configure our net work as follows.


--->Router---> Switch that connects to all phones
Cable Mode --> Unmanaged switch--|
--->SonicWall--> Switch that connects to computers


I configured the router for the phones and that works with no problems. But, when I configure the SonicWall with the information provided by our cable modem provider it worked but the SonicWall said it needed to restart after configuration so I clicked restart. Then the the internet connection wouldn't work and I couldn't get back into the SonicWall.

After numerous attempts at powering down the SonicWall and switch I finally was able to access it again and then the connection disappeared and finally I got access back again and reset everything to how it was on the T1 line.

The WAN setting on the SonicWall are as follows:

SonicWALL WAN IP (NAT Public) Address: I set this to an IP address in the range provided and made sure it was different than the one in use by the router for the phones.

WAN Subnet Mask: I set this to the subnet our provider sent listed

WAN Gateway (Router) Address: I set this to the Gateway address our provider listed

DNS Server 1 & 2: Set to what our provider sent over.

There is also an option for LAN settings.
SonicWALL LAN IP Address: I left this as it was
LAN Subnet Mask: I set this to the subnet mask our provider listed.

From reading the setup guide for the SonicWall everything seems to be correct but then I am not able to access it nor do we have an internet connection. The phones still work so there is connectivity to the modem.

I also tried connecting directly to the SonicWall rather than through a switch with no success. Reseting seems to eventually work but I am not sure if that worked or if it was something else.

I am not sure what additional information would be needed so if you need something else please let me know.