I have a (crappy) Samsung GT-I5500 phone (also known as Samsung Galaxy 5, Samsung Galaxy Europa and a bunch of other names) with Android 2.2.
Since about 2 months I am having problems sending text messages (SMS). Most of the time they just remain in the status "Sending...". Sometimes, but not always, after a long time (multiple days) the recipient finally receives the message.
To check the origin of the problem, I've switched SIM cards with my girlfriend, and then, strange enough, both worked (my SIM card in her Iphone, and her SIM card in my android phone). Putting my SIM card back, the problem reappeared.
Are there any specific settings I can check?
(However, I don't remember changing any of those earlier)