Texts received ok but not able to send texts either to reply to a selected one , or "write new"

[Georgina36]

This basic Sony Ericsson 2G phone works fine : calls made and received ; texts received ok , but i cannot reply to a selected one , or select "write new" to text a new number ; a received a scam call from someone pretending to be from O2 has the device been compromised? Prior to the blank section ready to write my text message , i get the "service centres" display with "add new?" written , and cannot get any further. What are "service numbers" ? I can visit an O2 shop if necessary.

[MI5 · Accepted solution]

@Georgina36 

You need to check the message centre number 

Guide: Text Message Tips (not sent or received) 

[Georgina36]

Hi , thanks for mailing ; i went into the Doncaster O2 shop to explain the problem ;it was not unfamiliar to them ;using their devices as staff members they checked and installed the correct service centre number;dont know why the original had disappeared. Then a replacement sim card was installed ;this took an hour or so to activate and the phone works correctly now.

Because the phone is not used much : basically one & sometimes two texts per day , and an occasional call , i still think to remain on "pay as you go" . As far as i can remember i was always on the classic one  but a text call to another mobile phone just now , for under a minute cost 55 pence and a text cost 30 pence. My top up card is the original one ; i am still using some credit that was transferred to the new sim card. New "pay as you go" top up cards were available at the O2 shop ; on the O2 site "pay as you go" charges are listed as  2 pence per text so perhaps a new top up card would benefit me. I will investigate this further but the original problem re the phone is now resolved ; many thanks to the two guys who replied.

[MI5]

@Georgina36 

Glad you are sorted. 

With regards to your tariff, there really isn't a low user option with O2 anymore. 

You can have the £10 big bundle which would give you free calls and texts but you need to add £10 every month. 

To get a low user tariff now, you need to look at other networks. 

https://www.1pmobile.com/

[Georgina36]

Hi yes , am checking it out ; now that i can send texts i can do the one to O2 for the code which a new provider requires ; i want to keep the phone's number. Thanks again.