Hmm. Interesting. I've only seen this when using a VPN. However, it can also be possible that this may be due to your ISP.
By that, I mean, by default your ISP will provide you with DNS service, as well as, other services ... like your WAN-side IP address. If that address is at all associated with the Dallas area, could be one reason why you are seeing this.
When using your phone with only a cellular connection or connected to another Wi-Fi network, does this issue still occur?
If either are true, then I would suggest performing a complete restore of your phone to put it back to its "out-of-the-box" configuration. After doing so, check to see if the issue persists. If not, then restore your phone's data from a backup. If it does, then contacting Apple support directly may be the next step to get this resolved.