The charity will receive 10% of all top ups on the network, and an additional 5% if users top up via its website.
It will offer two sim-only packs and four handsets, including the HTC Explore and Samsung E1080. Two phones with larger buttons and magnifying glass feature will also be offered for visually impaired people.
It claims that calls and text charges are up to 40% cheaper than those on major UK networks.
Calls and texts start at just 7p per min and 5p per text to other RSPCA Mobile users and 14p per minute and 7p per text to other networks.
Andrew Lyons, corporate account manager at RSPCA says: “As for many charities, this is an incredibly tough time for the RSPCA so we are always working on new fundraising ideas. Costs are increasing all round and at the same time members of the public are also feeling the squeeze and finding it harder to make donations. The RSPCA Mobile service offers a very simple way for people to incorporate giving into their everyday expenditure.
RSPCA Mobile will initially launch as a pay as you go service, but the charity plans to roll out a pay monthly service.
The charity will also sell a range of mobile phone covers featuring puppies, kittens and guinea pigs for iPhone, Blackberry and Samsung Galaxy S II phones.
The RSPCA Mobile network is hosted in partnership with Shebang Technologies Group, which owns Go Mobile and Affordable Mobiles.co.uk.