Assuming we're talking about the same panel (HestiaCP), and that their demo is not outdated, I poked around in it's demo and was able to find out that you can change the PHP version by editing the server (going to the server by the gear icon, then configure / alternatively the URL should be https://panelurl:port/edit/server/, for the demo it was https://demo.hestiacp.com:8083/edit/server/), clicking the "web server" section, and it should show the installed PHP versions , should look something like this:
If there isn't such an option, or I got the wrong panel, I'm sorry.
It doesn't seem to have the version you want (at least the demo, no idea how your server is configured and if you're able to change that from there), but you could try 5.6 and see if it works.
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I think you may be a little confused, understandably so as I was a bit confused too. infantex.mx pointing to Tommy, while infantex.com.mx points to the new VPS, seems to be the intended behavior. From what I've understood by what infantex said here, the first domain is set to still point to Tommy to help indentifying the problem, while the second (as the main site?) is pointing to the VPS. Quoting:
I fear my "explanation" might be more complicated than the initial messages, and @infantex please correct me if I understood it wrong.