bOnline Pay As You Go is the cheapest business phone system on our list, costing just £6 per month per user. It comes with a decent range of basic features, such as hold-music, company hours, and localised phone numbers. However, it may not be the best option if you have complex needs or are looking to scale. If that’s the case, we’d recommend 8x8 or GoTo, which both cost only marginally higher than bOnline, at £10 per month, per user.