Some tips when you want to delete more than one text messages (SMS) at time on Nokia 5800 mobile phone.
A) To delete all messages : Go to messaging --> Inbox --> Options --> Mark All --> Press the delete icon. This will ask to delete the selected number of messages. Press Yes to delete all on No to cancel the operation.
If you want to delete some selective message using above procedure instead of "Mark All" select "Mark" for the currently selected message. When done marking press delete Icon to delete all selected messages.
B) Delete all message from a specific sender : To do this you will have to enable grouping of messages. This will enable grouping for messages based on date, sender, subject and message type.
To enable grouping of text messages go to --> Settings --> Phone --> Application Settings --> Messaging --> Other. Here set the value of "Show Messages in groups" to "yes". Return back to your Inbox , you will find message are now coming in groups by date. Now go to options and select sort by as "Sender". You will find all your messages are now grouped by Sender. Select the sender name for which you want to delete all messages and click the delete icon. Press "Yes" to delete all "No" to cancel the operation.