If it would be possible to have more than a single match, you may try:

Formula in B2
:
=TEXTJOIN(", ",,IFERROR(FILTERXML("<t><s>"&SUBSTITUTE(A2,", ","</s><s>")&"</s></t>","//s[starts-with(., '+357 99') or starts-with(., '+357 97')]"),""))
If you don't want to use TEXTJOIN()
but you need to split the results, you could try:
=TRANSPOSE(IFERROR(FILTERXML("<t><s>"&SUBSTITUTE(A2,", ","</s><s>")&"</s></t>","//s[starts-with(., '+357 99') or starts-with(., '+357 97')]"),""))
If you don't have Excel O365, you can use:
=IFERROR(INDEX(FILTERXML("<t><s>"&SUBSTITUTE($A2,", ","</s><s>")&"</s></t>","//s[starts-with(., '+357 99') or starts-with(., '+357 97')]"),COLUMN(A1)),"")
Drag left and right.
Note FILTERXML()
is available from Excel 2013 onwards.
If only a single value of both excists, the other answer will handle just fine. Also, unfortunately "SPLIT()" is not an Excel function, but if you are interested in how FILTERXML()
can be used to split a string, you may find this interesting.