Signal app is sending messages from different phone number in Dual Sim Phone

I have a Fairphone 3 with E/OS and DUAL SIM. I have the Signal app installed for my second SIM card, which is private phone number.
When I sent messages with Signal it shows the name of the provider of the first SIM, in the case BEN, which is my business phone.
In the screen where one starts to type the message is says: unsecured BEN Nl.
People report receiving messages from Signal as a normal message from the default messaging app.

I have the second SIM as preferred number for calls and sms.

Any suggestion is very welcome. Thanx a lot.
Have a good day!

I uninstalled en reinstalled the Signal app. Now it seems to work well… for the moment.
I wonder if it has something to do with switching between which phone number one uses to call from in the setting menu. I will report any changes.

Regain your privacy! Adopt /e/ the unGoogled mobile OS and online servicesphone

Does Signal use the data setting for sending messages? In that case what is your data setting? On SIM 1 or SIM 2?

Thank you Lidwien. I don’t know if signal uses data setting for sending messages. I have no data bundle on the business phone, so I’ve shut that down under settings > network> BEN NL. I am only using data on the private number.