SMS messages won't delete no matter what

I have a phone which has thousands of SMS. Now it's very difficult to delete them all and the SMS app always hangs. I have tried the following to no avail: - Select All SMS > Delete - Downloaded SMS Backup & Restore App and used it's delete function - Downloaded Super SMS Quick Delete App and used it's delete function They all just hang. I am also trying to "Clear Data" the Dialer Storage App but it's not pressable, even after "Force Stop". How can I make the Clear Data button pressable? Or, is there another way to delete all SMS aside from Factory Reset?