Sip trunking recommendation

I’m looking for a sip trunking service provider for my Asterisk hosting services to enable me to resell PBX type voip services to some very specific industries.
Can anyone recommend some reseller company they’ve dealt with for a while and they’re happy with their service and reliability, I would like to deal with a company that offers good value, good service and Ideally would have an API to automate order fulfillment.

I appreciate anyone’s input very much.

Where are you based? I can recommend some UK companies but that probably wouldn’t be much use if your not here.

Yah depends on your location. which destination you are looking for?