Since it is a fixed data you don't need to assign a customer to be able to print that info. You might have other options. For example you can use ticket tags. Instead of choosing a customer you can use "Update Ticket Tag" action. We don't need to create ticket tags when we use them through actions.
For example create a new action, name it as "Set default customer info", action type will be "Update Ticket Tag", Tag Name will be "Customer Info" and finally enter what info you need into "Tag Value".
Create another action, name it as "Clear default customer info", action type and tag name will be the same. This time just input a single "space" in "Tag Value" area so it will clear that ticket tag.
On "Ticket Created" rule, execute "Set default customer info" action.
On "Customer Selected for Ticket" rule, execute "Clear default customer info" action.
In printer templates you can print that ticket with with {TICKETTAG:Customer Info}. For example
[Customer: {TICKETTAG:Customer Info}]
will only print "Customer:" suffix if a Customer Info exists. Square brackets does that.
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Another solution might be designing a separate ticket printing template and hardcode that info on ticket header. "Tag" column in printjobs is used to filter maps by Ticket Tags. For example if you enter "Default Customer" there and if there is a ticket tag named "Default Customer" in ticket that line will work. So you can have two maps on your "Print Bill" print job. One of them will be the default template and the other one will be the customer info hardcoded bill template. This template will contain a specific ticket tag and it will execute if that ticket tag exists.
Sorry I can't create a step by step tutorial atm but feel free to ask when you need.