Bulk Update Error

Hello everyone,

I'm having a problem using the bulk update feature. I am trying to update the properties of some contacts which is done in a for each loop which

I have a map containing a list of items to update e.g

Nb: Numbers have been edited for privacy reasons but assume each number is different

updateList = {"id":"5030199000000455770","Phone":"1868-6255555"},{"id":"5030199000000455769","Phone":"1868-6255555"},

{"id":"5030199000000455768","Phone":"1868-6255555"},

{"id":"5030199000000455761","Phone":"1868-6255555"};

When I call the zoho.crm.bulkUpdate("Contacts", updateList) I get the following error:

{"code":"INVALID_DATA","details":{"maximum_length":100,"api_name":"data"},"message":"invalid data","status":"error"}

I'm troubleshooting the issue but any help getting this sorted will be appreciated. Where do I start?