iPhone, default language should be English not Spanish. I have a Panamanian Sim card inserted.

Seems you can just change the language on your iPhone:

Eg: Apple Support's online article: Change the language and region on iPhone - Apple Support

says:

1. "Go to Settings  > General > Language & Region.
2. Set the following:

• • The language for iPhone.
  • Your preferred form of address. (Choose feminine, masculine, or neutral. Turn on Share with All Apps so all apps personalize how they address you. Available for some primary languages, for example, Spanish.)
  • The region.
  • The calendar format.
  • The temperature unit (Celsius or Fahrenheit).
  • The measurement system (metric, US, or UK).
  • The first day of the week.
  • Live Text (text you can select in images to copy or take action on).

To add another language and keyboard to your iPhone, tap Add Language, then select a language".

Ummm .... Sorry that hasn't helped ... if you haven't already, you might want to try restarting your iPhone (deletes temporary files, updates recent setting changes, etc., and often restores order if something is not working as expected.

How to: Restart your iPhone - Apple Support

Re: "I do have a Panamanian Sim card inserted"

I do not know whether the SIM card may over-ride the iPhone settings .. have no experience of this.

Wondering whether your SIM-provider can help,

or

whether you may want to check with iPhone Support ... there is a "Get Support - start now" link (online chat, phone, email etc.) at the bottom of their website (link below):

iPhone - Official Apple Support

Thank you kindly for your replies, and for your patience :-)