www.call08.com give you an 0800 number with 1000 included incoming minutes for £4.95 per month + VAT. Once those are exceeded they charge 2p per minute (I'm not sure how much your provider charges if you run over the 1,000 free minutes per month).
So you seem to need the service you have paid for to still be in business in 31 months time (31 x 4.95 = £153.45) to be ahead of paying monthly with
www.call08.comPerhaps this is a new 0800 call vending business and typically they offer these Lifetime type packages (I have one on an advanced tv hard drive recorder called a Tivo that had a £10 per month sub or a £200 for "Lifetime" service option back in 2002 that I am now quids on after 70 months of Lifetime service for £200) in order to get cash in the door to help start up their business. Later if they are successful they will only sell on the
www.call08.com basis of a monthly fee. Clearly if they sell too many of these lifetime 0800 deals and then don't get enough monthly paying customers later on they could go belly up and your lifetime 0800 number is then worth nothing. In effect its something of a gamble. You could end up very handsomely in profit compared to a
www.call08.com deal after 5 years and there again you might not.
Don't forget that with more and more people switching to contract mobiles and then eventually calls on the internet via voip our useless regulator Ofcom has seen to it that calls via those means to 0800 numbers are not free. I am sure calls to 0800 numbers from ordinary landlines and BT Payphones will remain free but both means of making calls are in decline so ultimately the number of incoming 0800 call minutes per month you receive will gradually decline with the passage of time.
On the other hand if you run a business from home and also give all your friends and family the 0800 number you can clearly do everything possible to maximise the number of incoming 0800 call minutes per months you receive.
It all depends how long the firm you bought the number from stays in business for at the end of the day...............................
As to Ofcom and them not knowing too much about your issue sadly that is an all too typical description of almost of any form of interaction between the general public and the bored, clueless and telecoms disinterested staff who Ofcom have employed to work in their so called Contact Centre. What a pity that the telecoms regulator seems to find communication to be such a difficult art to master.