Maybe resort to using a recruitment agency? (Which would be a last resort for us too!)
Paul.
Be wary
As an ex recruitment consultant i hated dealing with sales roles especially high volume sales. If you do use an agency use a sales specialist one and get some form of rebate guarantee.
Also quiz them over applicant sourcing - if all they are doing is smashing ads out on Indeed etc and sifting the responses then be prepared to have a lot of timewasters who will not get back to you on interviews or not turn up.
I would suggest getting 2 agencies (don't do a sole agency as it reduces incentive of the recruiter to really graft unless you put a v.strict say 2 week limit to get a shortlist and arrange interviews before you talk to others) - tell both that you will not go to other agencies and if they promise to fully brief applicants up front including on your name before sending the cv and reasoning on why that candidate is great then you promise to interview their 3 best applicants out of hours if need be but within 48 hrs of the introduction. Tell them if you receive the same cv form both agencies you will ask the applicant who told them your name first and go with that agency as having made the effective introduction.
Anyone who baulks at that isnt worth talking to - the decent recruiters will take it as a meaning they won't get shafted by someone else throwing mud at the wall.
Also ask the recruiter what you can do to make the job more attractive to applicants - tell them your salary budget and what if any movement there is on it. Tell them if you have to have to push that there will still not be extra money to pay a recruiter so don't waste their time sending those 20% over budget in the hope you take them on and they make a bigger commission.
The cost of using a mud slinger promising 10% fee can be far higher than a decent consultant who charges 20% of base - remember the right person will make you a lot of money in higher sales going forward.
The other alternative is engage a cheap one but tell them exactly what you want them to do - as in just say "i want you to scour the internet and world for telesales people, send me any that meet these criteria having verified X, Y & Z and I will do the rest but you are only getting £2k 30 days after they start and if they leave for any reason other than redundancy within 90 days I want my money back
There is not really much in between