@dannmatmum cannot roll back firmware by official means. As long as it was a genuine Samsung update unlikely to be linked. Texts can be reported to your provider via the number 7726 (spells spam) and reported to texts/emails can be reported to the National cyber security centre.https://www.ncsc.gov.uk/collection/phishing-scams
However may be an idea to wipe the cache partition which deletes temporary files by following steps:
1. Turn off the device.
2. Connect To Computer or plug in USB-C Headphones , Press and hold the Volume Up key and then press and hold the Power key
3. When the Android logo displays, release all three keys.
4. An 'Installing system update' message will show for 30 - 60 seconds before the Android system recovery menu options appear.
5. Press the Volume down key several times to highlight wipe cache partition.
6. Press Power key to select.
7. Press the Volume down key to highlight yes, them and press the Power key to select.
8. When the wipe cache partition is complete, Reboot system now is highlighted.
9. Press the Power key to restart the device.
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 5.0,Android 13 .