IPhone 3GS signal drop and late texts.

My IPhone 3GS seems to have random signal loss, in places where it has previously had good signal. I have noticed that there is no pattern to where I lose signal, but it is reletivley frequent.
My iphone also sometimes does not recieve texts sent to me for a couple of hours after they were sent. It does not always happen, but I can have as many as five texts come through hours late.

If anyone is having similar problems and/or has found a solution for this, any help would be appreciated. Thanks.