The minimum interval between bumpings is 24 hours (rule 6 in the support FAQ).
You are using an obsolete version of Asterisk.
You have two dialplan lines with the same extension and priority.
I don’t know what TF stands for.
You haven’t told us what you’ve already tried.
The best way of finding out how to conect to a SIP based PSTN access provider (often mis-named DID) is to ask them. If they provide a business service, they should be able to tell you how to configure Asterisk, although they may give you instructions for a more current version. The details vary between provders.
on above config, 8588888888 is sample TF or Toll Free number and 115 is my extension that should receive calls. The provide said that they already register our asterisk public IP to receive calls from DID and TF.