O2 has issued a recall for around 28,000 O2 X1 handsets after a number of issues were identified with the flip phone.

[...] O2 is recalling this phone and offering customers a new replacement phone free of charge. For safety reasons O2 recommend that you do not re-charge your X1 phone and return it to us together with charger for replacement immediately. In extreme cases this fault may cause overheating and fire when charging.

O2 customers who have this handset should contact O2 to arrange for the return and replacement of their existing handset.