A third of smaller businesses think mobile phone companies are ripping them off.

In a survey by telco RSL Com, one in three companies employing less than 100 people were disgruntled that their mobile phone providers had kept new, cheaper tariffs from them after they had signed contracts.

When UK firms that aren’t the size of Sainsbury’s grow, their business needs change drastically, and it seems some firms are concerned they are not getting the ongoing service they need while they grow.

But mobile firms are sure they offer decent smaller business services. Vodafone said it offers business plenty of advice and the ability to get “tariff health checks” to ensure companies get a good deal.

The main problem, said a Vodafone spokeswoman, could be that smaller companies start out with a mish mash of phones from different companies. “Obviously we’d advise them to standardise with one provider and they’d probably get a better deal,” she said.

Vodafone said smaller businesses would normally be allowed and even encouraged to change to the most suitable tariff. In the hyper-competitive world of mobile phone services, this is done to keep customers, even though they may end up spending less per person.