For Case insensitive regular expression(Regex): There are two ways by adding in your code:
flags=re.IGNORECASE
Regx3GList = re.search("(WCDMA:)((\d*)(,?))*", txt, **re.IGNORECASE**)
The case-insensitive marker (?i)
Regx3GList = re.search("**(?i)**(WCDMA:)((\d*)(,?))*", txt)