Tried the same and failed. The response from Safaricom is as below:
“Thank you for your email. We sincerely apologize for the delayed response.
We wish to bring to your attention that T-Mobile, AT&T USA shut down their 3G on 22nd February, 2022 which supports voice calls. AT&T is currently having 4G and 5G technology ony. The two technologies do not support voice call and sms until we launch VoLTE with the partners.
If you want to perform voice calls you will need to manually select T-Mobile, though very expensive.
We sincerely regret any inconvenience caused.
Thank you and stay safe!
Kindly take a few minutes of your time and rate the quality of service we offered on email. Please use the link - https: //www.safaricom.co.ke/emailsurvey/ “