detect and extract phone numbers

I am using a software integration platform to connect to a Google calendar and read appointment events. Each event has a small description and phone number in the Summary and I need a regular expression to extract those phone numbers.

The problem is that each person entering an event, formats the phone number differently. Some phone numbers have spaces, or country prefix, and in some cases, there are other (irrelevant) numbers in the Summary also. I don’t mind keeping the country prefix if they enter it, but I do need to detect what’s the phone number.

So, here’s some information on the numbers

- If the user entered a prefix there will be a 357 or 00357 or +357 in the summary.
- After the prefix (if it exists) each phone number will start with 94 or 95 or 96 or 97 or 99.
- Then 6 more numbers will follow.
- There could also be spaces between the numbers

Eventually a correct phone number will be

99123456 or 35799123456 or +35799123456
99 can also be 94 or 95 or 96 or 97

I don’t know if this is too complicated or if it’s even possible to create a regex to correctly extract the phone numbers. Any help is appreciated.

Thanks