can I put a phone number on a message

[ar4-64]

can I put a phone number on a message

[thedemon2014]

eBay does not allow the exchange of contact details between buyer and seller until after the buyer has committed to buy the item, by going through eBay checkout.

https://www.eBay.co.uk/help/policies/member-behaviour-policies/membertomember-contact-policy?id=4262

[ruby*tuesday]

No you are Trading illegally offering a Mac Repair Service and requesting Buyers to Message you and adding a Mobile phone number. 

You can give Buyers your Phone Number once they have Purchased the Service but before they Pay.

You need to correctly Register as a Business Seller. 

@plpmr

[*guinevere*]

That is not allowed as it is classed as exchanging contact details and ebay would see it as trying to enter into an 'off ebay' deal, and therefore doing them out of their fees.

Ultimately you could get your account closed down.