I found it very strange when I didn't find any setting to set the sms center number in the default android sms app. For most of the providers it usually obtain the SMSC setting from the operator and set it internally. But it would be great to provide an option to change it in the setting, in case I want to use a different message center number.
If you facing issues in sending or receiving sms, your message center number might be empty or wrong! Like my case, it sometime happens because of the poor service providers like bsnl.
You can follow the following steps to check and update it.
1. Dial *#*#4636#*#*.
2. Select Phone Information from the Menu.
3. Scroll down to the "SMSC" setting. There are two options refresh and update. Try refresh to check if it gets the message center number from your operator. If not, then you can call your operator to get it, and then update it.
Happy Messaging on Android!!