I have all of my credit cards and bank accounts setup to send message alerts to my phone whenever there are any charges to any of my accounts and the alerts from multiple banks and credit cards have always worked as expected. I ported my cell # to Xfinity Mobile from T-Mobile in 2/2020 and was a bit surprised that the banks knew that I had changed cell service providers and required that I re-validate my phone which I did and the alerts from all of the banks and credit cards started working again after I revalidated except from Ally Bank. To reiterate, my phone number did not change after I moved to Xfinity mobile.
I called Ally Bank. Ally said that Xfinity mobile isn't a supported cell service provider even though Verizon is supported by Ally and Xfinity Mobile uses the Verizon network. Ally said that it isn't the network that is a problem but the cellular service provider (in this case Xfinity) that is blocking the messages. Ally said that Xfinity would need to do something (not sure what) to enable the alert messages to pass.
In summary, I am asking Xfinity Mobile to investigate and made required changes to enable text alert messages from Ally Bank to be delivered to my phone.