I had extremely disappointing experiences with One.Tel.
Like many others, I was excited about all the low prices – then realized, that in one category (local calls) I was charged more than 100 % the promised rate. I tried to complain – and never got a message back from them. As time went by, I sent 10 e-mails and 2 printed letters, all in vain. At last I asked Oftel for help, they send them another letter, and to this day, One Tel hasn't replied to Oftel either.

Stupid me had also established a direct debit for One Tel – without reading their gagging provision (in the small print), i.e., if you cancel the direct debit (even if you give plenty of notice!) they'll charge you hefty administrative fees.

So in the end, I did all I could do – left them. Thank God I didn't lose an absolute fortune, but if you want to do yourself a favour – don't go for One Tel. Cheap offers don't help you if the company is dishonest.