$string = 'Thank you for calling 555-5757 your order total is $123.32'
$string -Replace "[0-9]","0"
Use the -Replace to Replace String using a regular expression
PS C:\> $string = 'Thank you for calling 555-5757 your order total is $123.32' >> $string -Replace "[0-9]","0" Thank you for calling 000-0000 your order total is $000.00