1a> MikroTik support only the display of 7-bit characters (as in CP470),
the remaining 8-bit are unsupported and € symbol (And be can insterted only by winbox and webfig because terminal do not support it)
is translated from winbox/webfig on hexadecimal value 0x80 (that is € on CP1252 and others).
Since there is not correspondence from various language on 8-bit characters, codepage is needed and what is, for example € on CP1252 is Ђ on another codepage.
1b> MikroTik do not support UCS-2 alphabet, if the message contain simply one UCS-2 character, all mesage is on UCS-2 format and MikroTik can not read it.
On GSM7 alphabet the only currency symbol supported are £ $ ¥ and the generic ¤
If € is used, can’t be encoded on GSM7, and the character is removed, or message is not sent.
http://forum.mikrotik.com/t/sms-charset-problem/74623/2
2> I do not know if MikroTik add sooner or later the support for the UCS-2 SMS, but actually you can not read or sent that characters.
At least must be implemented a method for read by AT commands the SMS memory and convert the RAW binary data to readable message,
and do the opposite to send the SMS with support for UCS-2
Probably using the API of the Huawei, is possible to send one message with “ñ” or “€” simply converting first the message with ASCIItoCP1252toUTF8.
If your codepage is not CP1252 / Windows 1252, must be done one appropriate function using the ASCIItoCP1252toUTF8 as base.