When we contact a business we've never used before, most of us are looking for a bit of reassurance that the business is professional and will do the right thing by us.
The larger and more professional the business appears to be (e.g. national toll-free 1800 or 1300 phone numbers, local landline numbers for multiple areas), the more comfortable we are about handing over our hard-earned cash. And even though it may be unfair, we'll often hesitate to contact a business if the only contact details provided are a mobile phone number or a free email address. That just looks unprofessional and untrustworthy.