Teams connection problem

Hello 

I have a problem to connect my @gmail.com address to Teams as a customer obliged me to pass throigh them to connect to the system. Since then, I need to hace a double check on security (through a system of code and through the mobile phone). Since yesterday it doesn't work anymore.
I would like to recover my direct possibility to connect to Teams without passing through the web site of my former customer (that means I need to do a complete reset and cut the link to the customer).
How can we do this ?
Thank you,
Regards,
Bettina