Mr Toplass, from Nottingham, claimed he was not told important facts about the contract he signed in February 2023.
He said he thought he was signing a two-year deal with Hii Com and did not know he was renting the phones under a finance arrangement with another company.
He had “completely trusted” the salesman, but lived to regret not reading the small print.
The contract stated that the equipment would be rented by a third party – the finance company Grenke – over 27 quarters.
Mr Toplass found he now owed more than £10,000, to be paid over seven years.
“They never at any point said we were entering a lease-hire contract,” he said.
“It’s morally wrong on every level. We do business and we are open and transparent with every one our customers. Upfront, fixed pricing.
“This business didn’t do any of that.”
Hii Com claims to have more than 3,000 customers.
The BBC secretly filmed a 90-minute sales pitch by a representative of the firm.
During the meeting, a would-be customer was told three times he would only be dealing with Hii Com. A lease hire agreement was not mentioned.