The charity is one of many to have used texting as a donation medium for fundraising campaigns, but with only about £1 of each £1.50 text donation reaching the cause, the charities feel they are being short-changed.
Annabel James, director of charities at GCAP Media, the owner of Capital Radio, which set up Help A London Child, is working both independently and with the Institute of Fundraising to create a charity rate that is more beneficial to the sector.
They have been talking to the major players in the mobile phone industry about the issue since last year, but little progress has been made - they are still waiting to hear whether the companies will introduce a discounted price structure for charities.
James said: "You only have to watch Big Brother or The X-Factor to see how immediate texting is. All charities should be able to make use of it for fundraising."
Part of the problem is that the costs of premium-rate texts are affected by the different parties involved in the market, from the phone companies themselves to newsagents selling top-up cards. Another difficulty is the fact that the various mobile phone companies cannot discuss or agree a common pricing structure without contravening competition regulations.
Representatives from the larger telecoms firms returned from the Czech Republic last week after hearing a presentation on a Donors Messaging Service, which provides a discounted price structure enabling anyone to donate money to charity by text. This could influence debate about the issue in the UK.
Separately, charities that want to experiment with text fundraising can take advantage of a month-long free trial of Iris, the online mobile marketing system from mobile marketing agency Incentivated.
The offer is open until 16 March and registered charities will be able to use the service before 16 April.
Jonathan Bass, managing director of Incentivated, said: "Mobile phones offer the most immediate and convenient way for members of the public to donate money to charity, wherever they are."