On Monday night and Tuesday morning telephone users settled into two distinct camps. There were those who reached swiftly for the dial after seeing TV and press advertisements for a new company, Esat Clear, and there were those who resisted ringing the freephone number.

The consumers who got excited by Esat Telecom boss Denis O'Brien's promise of reductions of up to 20 per cent in the cost of private phone calls are, it appears, a more chatty bunch, spending more time either on the phone or in cyberspace.

Mr O'Brien's initial offer in the newly liberalised telecommunications climate targets only the 450,000 people who spend more than £100 on their twomonthly phone bill. This defied expectations that all phone users in the State would be offered an immediate alternative.

The remainder comprise the 65 per cent of Telecom Eireann customers that are more cost-conscious or have fewer teenage daughters with phones permanently attached to their ears. They will not benefit from the Esat deal.

The launch of the Ocean package was more subdued. Owned by British Telecom and the ESB, the company also unveiled a range of services directed at both business and residential users. The Ocean Link services are not restricted to those with larger bills, but the Ocean package is geared towards users who make regular calls to mobile phones or international destinations.

Esat Clear and Ocean are among 29 companies that this week received licences to operate in direct competition with Telecom Eireann, opening the telecommunications industry in this country to full competition for the first time. However at the moment it is only Esat Clear, Ocean and Telecom Eireann that are fighting for the attention of residential phone users.

The question is: Should you stay or should you go?

If you spend more than £100 every two months, Esat Clear maintains you should jump Eireann ship. Key to its package is the fact that it charges per second, unlike Telecom Eireann, which has a per unit policy.

With Esat Clear, according to the ads, "you only pay for what you say". The company estimates that 40 per cent of the call charges on Telecom Eireann bills are for unused time, representing the potential for significant savings.

Another factor is its treatment of the whole island of Ireland as one region, entailing an end to trunk calls. With Esat Clear, which also offers an Internet service, local call rates apply everywhere in the 32 counties and will be charged at a rate of 5.1p per minute peak, or 1.8p per minute at the weekend. This is expected to attract many heavy users, disgruntled at having to pay extra to phone a neighbouring county.

But it would appear that the real savings will be made on calls to Britain and other international destinations using Esat Clear. A 10-minute call to Britain at the weekend using Telecom Eireann costs £1.50; Esat Clear charges £1 for an equivalent call. Chatting for 10 minutes in peak time to a friend in the US will set you back £2.90 with Telecom Eireann while with Esat Clear it would cost around £2.20.

IF you decide on the changeover, a call to Esat Clear (1800-313 321) or Ocean (1800-263 326) sets the process in motion. It is important to note that swapping phone companies does not require a new phone line - the customer is still renting the line from Telecom Eireann while the new company will feed off the existing network. This is made possible by a simple piece of equipment the size of a pack of cards which, in the case of Esat Clear, is installed free of charge for residential customers. When calls are made, they are rerouted to the new company, and while customers still receive two-monthly line rental and/or phone rental bills from Telecom Eireann, they will receive a separate bill from the relevant telecommunications company detailing their calls.

The same applies for Ocean Link customers, although there is an initial subscription charge of £20 for the service. The company's call charges are slightly higher than Esat Clear in some cases but consistently less than Telecom Eireann's and are also billed per second. A 10-minute call to Britain at the weekend costs £1.30 with Ocean and a 10minute peak-time call to the USA costs a competitive £2.15. Along with its two competitors in the residential market, Ocean also has a number of discount schemes.

Far from taking this onslaught lying down, Telecom Eireann has spent the week illustrating how in some cases it's better the devil you know. A spokeswoman listed at least three instances where the customer pays less with Telecom Eireann.

The first is for a three-minute local call, which costs 11.5p peak time with Telecom Eireann but around 16p with Esat Clear. The second is for a 15-minute local call after 6 p.m., which with Esat Clear comes to around 37p but with the State-owned company costs only 11.5p. The final example is a 10-minute national call at weekends, which costs around 18p with Esat Clear but just 11.5 with Telecom Eireann.

Telephone users might be advised to sit tight and wait for the full picture to develop. Telecom Eireann has already announced its intention to introduce per second billing and its intention to further lower prices over coming months. Meanwhile, more of the 29 licensees will begin to launch on the market, leading to even greater choice.

To switch or not to switch? It's your call.